So demonstrate it?
From personal experience I can say that non-religious people tend to have no problem with gay people and are less likely to use sexual orientation as an insult. Kids who grew up in households where being homosexual was viewed as disgusting and wrong are more likely to employ gay slurs and attack and hurt other kids who are perceived as different. (Different = bad, gay = bad, it is easy to see why this becomes such an effective bullying technique.)
Knowing that people with strong religious backgrounds are the most likely to see homosexuality as wrong, and that most religious people in the united states are christian, it makes sense that these particular bullies are coming from christian households.
If you can dispute this logic at any point, please do so. Otherwise I must agree with the OP--the views of the parents are being used by the children to ostracize and bully others, and makes them think it is okay to do so because the kid in question is effeminate and different. And if people are being hurt, physically, mentally, and emotionally, just for kind of looking like they belong with your group, I'd say that's an issue the group in question can legitimately pursue.
It is true that bullying is going to happen, but children don't need help or encouragement from their parent's political attitudes.