It's a line from The Music Man. "We've gotta protect our children!" In the movie version Buddy Hackett shouts the line at a town hall meeting, after Professor Harold Hill gets the townsfolk all riled up about the pool table that came into town.
What's wrong with a pool table? Nothing. But the little town in Iowa had never seen one before, so its residents were easily duped into believing it was evil because it was different. Professor Harold Hill exploited their ignorance to sell his band instruments to protect the kids.
A variation of this tactic is now being used to support Proposition 8. Oh-My-God if men can marry men and women can marry women they'll be telling our kids about it in school! And that would be HARMFUL!!!!
Well, they don't actually say it'll be harmful. There's absolutely no evidence to suggest that it would be. So they can only imply it by screaming some variation of the alarm "We've gotta protect our children!"
Same-sex marriage is no more a danger than a pool table, and the moral agenda of the pro-8 movement is as bogus as Professor Harold Hill's boys band.