My Catholic father has really been hurt that I espouse atheism. He likes to say things like "You're not REALLY an atheist, because you celebrate Christmas. You put up a nativity scene!" When I say "Yeah, but I decorate with Santa Claus's, too, and I don't believe in him either." he (understandably) gets a little offended, and starts to go off on how Saint Nicholas was real.
Anyway, when I questioned him on "Why YOUR God, and not Hindu? or Allah? or Ra?" his response was that there are no other gods. All these different cultures are just worshiping the same ONE god in different ways. Kind of like a much much broader view of Islam, Judaism & Christianity all descending from Abraham.
How do you argue against that sort of approach? He was a biology teacher, and finds zero conflict between his faith & science. He believes that evolution is how god created us. He believes that science is the language with which god made the universe. He comes back to the "ultimate cause" argument (why something instead of nothing?). When I come from the perspective of a lack of evidence FOR belief, he goes to the argument from personal experience.
I've debunked a lot of his approaches about argument from design (that 'random' chance couldn't build a complex eyeball, it must have been designed to evolve that way - mental contortions anyone?).
Any thoughts on an effective way to support atheism in the face of generic "everyone is right" theism?
Rational people can hold irrational beliefs. Does your atheism really need support? I take that maybe you mean to ask if there is a compelling way to drive home your beliefs to another to change their mind? I don't know of any. People are prone to delusion and rationalizing things to support that delusion. It doesn't just happen with theists. Watch American Idol auditions and you'll see it there where someone is convinced of their talent, gets rebuked, and then makes excuses as to why the judges can't see it or refuse to acknowledge it. I hate American Idol, but the analogy fits. The more intelligent the person, the better they can rationalize. That may seem counter intuitive, but it is true. Your dad is a biology teacher and has to perform all sorts of mental gymnastics to hold mutually exclusive viewpoints at the same time.
The best thing you can do is be proud of your non-belief (you escaped indoctrination, something to be very proud of!), educate yourself, and be a moral person. What other people believe is up to them and there is not much you can say or do to convince him otherwise. Until he wants to honestly seek the truth, he is lost to his delusion.
Does he accept evolution or not? You say he does, but then he uses the 'you can't get an eyeball from random chance!' line other people ignorant of evolution use.
You could start with a simple example about the contradictory nature of these gods. Was Jesus the son of God or not? Islam and Christianity disagree. Push for a one word answer. Whichever he gives, he'll have shown one religion has it wrong straight away, all by himself.