Religious morals fail because they are self defeating.
Honour your parents, but don't steal. What if your parents tell you to steal something? What if they tell you it isn't really stealing because they thinks its theirs, but you disagree? You can either disregard your parents or disregard theft. And there is not higher power to appeal to because apparently thins god is so far beyond you that you couldn't possibly comprehend their motives so your only recourse is to follow the rules that they left behind in some rather dubious methods that have been proven suspect by all the opposing religious texts that turned up AND ARE BELIEVED! Or hey, why not just pick and choose what seems to make sense because hey, gods must be reasonable, right, well, except for being beyond reasonable due to some state that makes absolutely no sense from any perspective, but that doesn't matter, because it makes sense from a perspective that only looks like it absolutely certainly couldn't possibly exist because a completely perfect being created a completely flawed one in a completely uncharacteristic, and largely impossible, act...
What if your parents are not religious, what if they specifically tell you that they don't respect religion, don't want you to have anything to do with religion, and then die?
Multiple conflicting religions, even if no religions actually conflict with your personal religion, prove that faith alone is insufficient, because it obviously failed all the people who were wrong. I believe that faith alone is insufficient, so I don't need even need reason to dismiss anything that requires faith. The simple fact is that without an externally verified encounter with a god it is foolish to accept that one exists.
Not that it matters, so long as nobody is willing to define god it really doesn't matter what it is. You could call a pet fish a god and it would be perfectly valid. If you want to discuss the creator of our world, that is fine, it is completely unnecessary and actually creates some problems... You want something that judges an afterlife? If it refuses to make the qualifications clear, say, by having dead people turn up from time to time to remind us, then I don't respect its judgements or its person. It is(or isn't) just another pathetic piece of this world that needs to be overcome... You want something that controls this world? You are better off learning to control it yourself, a little control is better than an imagined little piece of absolute control... You want the patron of humanity to guide you? Find a target you can actually study and understand, instead of some amorphous blob of hypothetical authority that is blatantly abused by anyone with the inclination...
P.S.
I hate ninja monkeys...