Many people - usually religious, right-wing "family values" types - claim that "homosexuality is a choice", and that one piece of legislation or another will "encourage kids to be gay".
This is the bit I don't get - even as a straight guy raised in a pretty liberal household, I've never once looked at the idea of hot gay buttsecks and thought "y'know, I think that's the sex for me!".
I'm straight and non-homophobic, but even offering tax-breaks and free ice-cream to gays wouldn't tempt me to indulge in hot man-loving.
I literally can't comprehend of someone examining their own feelings and deciding homosexuality was a choice, unless they're naturally inclined that way themselves and in viciously deep denial about it ("it's got to be a choice, so I can choose not to be gay!").
So when they say that X or Y will encourage homosexuality, what they actually mean is that it will encourage people who are naturally that way inclined to not live their lives miserable, unhappy and in denial, never knowing the companionship they crave and at constant war with their own essential nature, until they become bitter and twisted by their own unrelenting self-loathing.
It therefore appears that the correct response to "Homosexuality is a choice" is "Well maybe in your case, ducky".