but...
I don't see any problem with people who actively believe there is not a God, when there is no evidence that there is one.
I do have problems with people who believe there is a particular type of deity, when there is no evidence that there is one, at all.
I even have issues with people who say "it doesn't matter" or "it isn't proveable". That isn't the issue - what's 'wrong' is actively believing in something that there is no evidence for. If someone is capable of that degree of mental tautology, they can be illogical, illiberal or unjust at a whim, imho.