Actually the thing about state funded things is that they should be voted on since they'refunded by tax payers' money.
However, I think people should be left to believe what they want, when it comes to things we're not really going to figure out any time soon, like the meaning of life and creation.
Chances are, my kids are going to a private school, but that doesn't mean I can't have a say in my kids' education, which is clearly the problem these days. Parents need to be more proactive in what they want their kids to learn, but not offensive: it's entirely your right to not want your child to learn about Creationism, but if someone else wants their child to, you shouldn't take that away.
Suffice to say, science is science...not theology. I do agree with Chewey, teaching theology would be interesting and probably beneficial, since it'd give children an open mind to religion at an early age.
I am entirely impartial to religion; I don't mind going to church with my grandparents if they want me to, but I don't really care about it one way or another. For one, I agree with what you say about using Religion as justification for discrimination, it's wrong and shouldn't be done.
However, I my self don't really want to support any group (that is not to say I don't support gay marriage) that will act on an irrational feeling, such as vandalizing property because you didn't get your way. If you want your cause to be taken seriously and widely accepted, you have to be serious, mature and cautious about the way you go through with it/present it to people who are afraid of it.
Like Skanker said about Switzerland, it was legalized and nothing happened to the opposition groups, but it sure did make a lot more people happy. That's good, and being the United States of America, that should be our goal by way of freedom.