On a side note, this is why I think the whole Rabbi Slifkin ban was instituted and why people are so afraid to accept the possibility that Rashi was a corporealist, because there is a lack of understanding of what traditional Judaism entails. Obviously, Judaism in the time of Dovid Hamelech was practiced differently than it is now, but that is ok because times have changed along with halachic decisions. Anyone who says that traditional Judaism has always been the same clearly knows nothing about the subject.
However, there is a big difference in the halachic changes that have been made throughout the generations in traditional Judaism and the breakoffs from traditional Judaism. There are always some basic principles that are kept within traditional Judaism that separates it from other branches of Judaism. The main difference for earlier sectarian sects was the text of the written Torah. The Samaritans and others did not even accept the text of the written Torah. They changed it to follow their beliefs, in our (Judaism's) opinion.
The next breakoffs, the Tzadukim and Karaites, did not believe in an oral tradition. This is where the Pharisees differed from them. Traditional Judaism follows in the steps of the Pharisees. The Pharisees believed that along with the written Torah there was an Oral tradition that explained the words of the Torah. This is where the Mishna, Gemorah and Midrash come from.
This is what traditional Judaism has today, an oral tradition (The Gemara). However, what is this oral tradition manifested as today? Well, we do not seem to paskin directly from the Gemara anymore. This is because there have been many great generations between us and the Gemara as well as many cultural and technological advances. Rabbis still use the Gemara in some ways, but almost every Posek uses Rishonim to back up their decisions. The way to derive halacha in this day and age seems to be by learning the Rishonim, the Rabbis of the middle ages, that comment on the Gemara as well as Achronim, Rabbis that comment on the Gemara and the Rishonim. This is what Rav Moshe Feinstein does in his Iggroes Moshe and this is what most great Rabbis have done for the past several years. Still, this is not the only defining factor, sometimes the idea of tradition (minhagim) comes into play. This is why Ashkenzic Jews do not eat kitniyos (things that look like wheat) on Pesach, even though there is no real halachic basis for this from the Gemara or most Rishonim. There is even a dispute when this Takana (Rabbbinical mandate) was instituted. However, no one is allowed to disagree with the Gemara, not even the Rishonim.
This leads us to the fact that traditional Judaism is a combination of the thoughts of the Rishonim and the traditions (Minhagim) that we have received from our forefathers. This is why Sefardim have their Minhagim that are very different than Ashkenazim. Also, this is why German Jews wait 3 hours between eating meat and milk, people from the Netherlands wait 1 hour and most other Jews wait 5-6 hours. These differences do not alienate these Jews from one another, but allow them all to fit nicely into traditional Judaism.
So, it seems to be that traditional Judaism is a combination of traditions passed on from father to son and Rabbi to student combined with strict halacha that is learned from the Gemara and Rishonim. Yes, the Gemara contained strict halacha, but it also combined that halacha with traditional teachings of its time. So really, the Gemara itself was similar to the Rishonim and current Rabbis in the sense that it created a tradition for its time. This is also why, in the time of Dovid Hamelech, they did not keep halacha in the same way we do now, there were different traditions (minhagim) that existed and a different interpretation of certain laws. There was no such thing as waiting between milk and meat, this tradition was not yet established. However, every generation has to take into account the traditions of the previous generation and maybe add or detract in some ways based on the needs of the community.However, why must we use the previous generations rulings to guide us? Why can't we just look at the Gemara and make our own decisions?
It is possible that a Midrash Tanchuma (Chapter 44:2) can answer this question. The Midrash tells us that when G-D was offering the Torah to the Jewish people He asked them who would be their guarantor that they would keep the Torah. They said Avraham, Yitzchak and Yaakov. G-D said that was not good, because they needed a guarantor themselves. This caused the Jewish people to respond that their children would be their guarantors. Immediately, G-D accepted this idea. From then on, the children of the Jewish people were forever indebted to keep the Torah of their forefathers or suffer the consequences.
This Midrash points out a very important idea, fathers can make commitments that are binding on their sons. This is why traditional Judaism is not just about strict halacha that is learned out from the Torah or even just the Gemara. Every generation can make binding agreements on the subsequent generations. All of the traditions (minhagim) are based on this idea. However, this is why every community has its own traditions and everyone follows their own Rabbi, because these traditions are no longer uniformed throughout the Jewish people, as they were in the times of the Sanhedrin. True, there are some traditions that were accepted by every community, but there are many differences that occurred, because of the diverse situations of every different Jew. The Sefardim created their own traditions while in Spain and that is why many of their halachas are different than the halchas made in Germany and Poland by the Ashkenazim. Also, the Taymanim (Yemenites) completely follow Rambam, because that is who their tradition is from. It is untenable to claim that there is a uniformed tradition with one set of rules.
With this in mind I think we can explain a couple of things. One is the idea of corporealism and the second is why people who reject the diversity of Judaism and the traditions in Judaism are fools. Firstly, in the time of Rashi there were clearly several Rishonim that held of corporealism. What this actually entails, I will not go into, but the Raavad CLEARLY says (Mishna Torah Hilchos Teshuva 3:7),
והאומר שיש שם רבון אחד אלא שהוא גוף ובעל תמונה. א"א ולמה קרא לזה מין וכמה גדולים וטובים ממנו הלכו בזו המחשבה לפי מה שראו במקראות ויותר ממה שראו בדברי האגדות המשבשות את הדעות:The Raavad seems to not believe in corporealism, but it is obvious that many of his knowledgeable contemporaries did and he considered them part of Orthodox (Traditional) Judaism. This leads us to believe that at this point in time, aka the Raavad's time, corporealism was an idea that was accepted in traditional Judaism. True, there were disagreements on this issue, but that is the same disagreement as Rav Moshe Feinstein saying a Jew can drink chalov stam (regular milk) and another great Rabbi disagreeing with him, according to the Raavad. According to the Rambam, however, these people were 'beyond the pale" of Orthodox Judaism. Nevertheless, just because there is a disagreement does not mean that one is representing the traditional view of Judaism and the other is not. The fact is that this was an idea that was not yet set in stone in traditional Judaism and either view was ACCEPTABLE. This leads me to believe that since Rashi is unclear on the subject, it is very possible that he believed in corporealism. It is also very possible that he did not. Either way, he would still be within the traditional Judaism of his time period.
(The Rambam states) that whoever says that there is One G-D, but he has a [physical] body and an image [is considered a heretic.] The Raavad says, why is this person called a heretic? There are many great and good people among us that go in this way of thinking because of what they saw in scripture and even more so from what they saw in the words of Aggadita (stories of the Rabbis) that confused the mind.
The second point of the people who reject the fact that there were several opinions and that there are still several opinions within Judaism needs to be explained. There are people that believe there is only one way to follow traditional Judaism. This is a huge mistake because it denies the fact that there is no communal body that decides on what the tradition should be. The truth is that there are many ways to follow traditional Judaism. There are many different theological, philosophical and general ideas that are within the parameters of traditional Judaism. This does not mean that all or even most paths are correct, but there is definitely more than one. For one person to think their Rabbi is the only way, that is narrow minded and foolish. My last example using the great Rav Moshe Feinstein will be this. How could one person say that following Rav Moshe Feinstein is the only way to be part of traditional Judaism while Rav Shlomo Zalman Auerbach's halachic capabilities are just as great? Or how could one invalidate Rav Ovadia Yosef?
Hopefully, one day, all Jews will be able to accept each other and not feel threatened by another group's way of life. We are all traditional Jews that want to serve G-D, now we have to work on our man-man friendship skills, as childish as that sounds. Once that works out and we can stop the ridiculousness and Chilul Hashems (desecrations of G-D's name) hopefully the Moshiach will come.
As a final point, I would like to add that there are several things that push a group outside of Orthodox (Traditional) Judaism. A group that ignores all previous halachas, Minhagim (Customs) and logical arguments can not be said to be part of Traditional Judaism, rather they would be reformers in line with a non-Orthodox or "Reform" type of Judaism. This is exactly what Reform Judaism is, something that decided previous transmission of the Oral Law is worthless and antiquated.
(Extra source for people who held of G-D's corporealism:
R' Moshe ben Hasdai Taku -- Ktav Tamim ed. Joseph Dan, pp. 7-27
R' Shlomo Simcha miTroyes -- Sefer Hamaskil
R' Joseph Ashkenazi -- "text published in Scholem, 'New Information'" (no I haven't read it)
Shadal -- Peninei Shadal, 316 )