I guess deities
could be true, but if they're true in such a way that it doesn't effect reality and there's no way to test it... well, to be frank, I don't care. I don't have the infinite amount of time and brainpower required to consider every possible "Thing that could be true but would not effect observable reality in any way", especially since the vast majority of them do not appear in any religion at all.
Even if they kindof effect reality but in a non testable way (such as Heaven and Hell) I don't see any need to speculate. A God (all powerful, all knowing, all good) who rewards you for doing good things is just as likely as a Devil (all powerful, all knowing, all evil) who punishes you for doing those things, after all.
Obviously whether it's useful for some people to believe in deities, whether religion has a positive effect on society and so on are all completely separate issues.
There are no good or bad morals. There's only morals, and a perspective. Something can be good for all, or good for a few, good for expansion, good for keeping the "race pure", good for happiness, good for stability, good for your country, good for all countries, good for you, good for others. In essence, nobody is evil, as everyone has some kind of rationalisation for his perspective.
It's interesting - I personally would say that some morals are relative, and others are more fundamental. The Golden Rule (which is common to basically all religions - I think humans realise that it's necessary for a remotely stable society, and therefore it got written into most religions) of "Do unto others as you would have them do unto you" or whatever phrasing you prefer... I think can be applied universally, and that "good" and "bad" can be to some extent defined by it.
So... for example, knowingly inflicting harm on someone else purely for your own gain would
always be bad if you defined "good" and "bad" in this way. Obviously there are loads of shades of grey (just because it's a universally applied morality doesn't mean everything has to be "right" or "wrong"), though.