Rambam-How do we view G-D- Yisodei Hatorah second halacha

In the Rambam's second halacha of sefer hamada he says,
ואם יעלה על הדעת שהוא אינו מצוי אין דבר אחר יכול להמצאות: 
"If one were to think that G-D does not exist then nothing else would be able to exist." 

What does he mean by saying that if one were to think that G-D does not exist? Shouldn't he just say that if G-D does not exist then nothing else could exist, why include a physical person's point of view?

The expression that "there are no Atheists in a fox hole" will help me explain what I think the point of this wording in the Rambam teaches us. The brain is a very complicated machine that the human being is created with. It has the ability to come up with so many different thoughts. For instance, Da Vince was able to imagine so many futuristic contraptions like the parachute and the airplane solely through his intellectual prowess. Also, in the world of philosophy people are able to come up with many ideas and one of those ideas is the concept of morals. However, the question must be asked, what are morals? Who can define what is moral and what is immoral? Can a council of elders decide what is moral for all generations? If so, why would future generations continue following morals that seem to obstruct their desires? Why is adultery immoral and marriage moral?

The only being that can define morals is the being that created all of the beings that would be bound by these morals. Otherwise, it would be like the USA telling England how to run their government. England would tell the USA, thanks but no thanks. However, the Government of the USA can tell the states within their government how to run.

Now, maybe we can understand what the Rambam might be saying. A person can not believe in an overall natural order that applies to all beings such as morals unless that person also believes there is a supreme being that created all of the beings in this natural order. Why would physics apply to one object in the same manner as it applies to another object if they were created separately and in different ways?

Going back to my statement of there are no atheists in a fox hole. By this I mean that everyone really, deep down, believes in an ultimate creator. Anyone who says otherwise chooses to ignore the facts that there must be a supreme being that created everything. However, the Rambam is telling us that an active disbelief in a creator of all things would lead this person to disregard morals and to live by his own rules as opposed to the communal and natural rules inherent in all people that are placed inside us by the creator.