Doodah wrote, if your morals are not tied to a system or belief or god or something you consider bigger than yourself, you are basically setting yourself up as your own god. you can change your morals whenever you want.
This depends on what you believe are the limits to what you can know and understand.
A person, presumably, could discover the principles of mathematics without a prior system of belief or god. The simple stuff, at least, such as 2+2=4.
And presumably, once having discovered that 2+2=4, it is well-nigh impossible to change your belief. People who believe that 2+2=4 do not on some sort of whim or delusion of self-grandeur change their belief into one where 2+2=5.
It is true that morality is not a matter of logical principle, such as mathematics (though some writers, such as Spinoza, held that it is). But nor either need mathematics be the one branch of reason where, once a belief is founded, it is essentially impossible to revise.
It's a bit like the principle of momentum, the theory of gravity, optical illusions or the Where's Waldo pictures. Once you see how it works, you pretty well can't see it any other way again.
Religion, on this account, acts as a visual aid. It points to moral truths which, once known, cannot be discarded. But as much as proponents would like to convince you otherwise, it is not the sole source of such truths, nor are all the things religion points to instances of such truths.
It is certainly arguable that a proposition such as 'civilized society requires a proscription against killing' is as epistemically sound as '2+2=4'. It is a conclusion virtually everyone, no matter what religion or whether they believe in one or not, reaches.
Yes, if you want the principle to be operative, you have to buy into the framework. For '2+2=4' to ever apply, you need to have counted at least two objects. For a proscription against killing to apply, you have to entered into civilized society.
But the truth of these principles is independent of the framework. Even if you are not counting objects, '2+2=4' is nonetheless true. Even if you live outside civilized society, 'civilized society required a proscription against killing' would still be true. These principles do not say that anything in fact exists or is the case; they represent relations between things, based on the inherent nature of those things, where this nature is recognized through observation, like where Waldo is.