I don't agree with using hypothetical bullying as a reason to prevent giving people rights. After all, historically we've made things legal
years before society caught up to it. If we waited for society to be fully comfortable with social rights moving forward, then giving women or blacks the right to vote would have taken infinitely longer. There is always the potential where if you legalize something, it can get more traction, representation or even just through contact help improve the overall opinion of it. Seeing more gay couples being just what all parents can be, healthy and supportive, might help people be more accepting of couples. It's not exactly unheard of for someone to change their mind about a topic simply because they met a member or members of that group and realized they're human.
Also, on a more grouchy level? It's laughable to assume that kids won't get bullied just 'cause they don't have two mommies or two daddies. Let's be real, if it's a huge deal in that area, the kid doesn't actually have to talk much about their parents. I have heterosexual parents, and I still avoided talking about them almost constantly when I was a kid. You know what most kids focus on when it comes to bullying? The super obvious. Hair, teeth, skin, clothing,
name, how they talk, etc. Here's an example. Who do you think is going to be bullied first and most? A kid with two fathers or the kid who has a mom and a dad, but is named
Gaylord Silly or
Steve Sharts?