Being gay is a fetish.

[Esquilax]

Now lets go on to what I am saying.  A lot of people would accept these premises.

Premise 1: Homosexual behavior is unnatural and immoral.
Premise 2: Gays choose to engage in homosexual behavior.
Conclusion: Gays make a willful choice to engage in immoral behavior.

So when someone says, "Being gay is a choice" they probably do not mean, "being attracted to the same sex is a choice".  What they probably mean is being gay means you have chosen to engage in immoral behavior.  The same people who claim being gay is a choice would probably also conclude that being a fornicator is a choice.

Try demonstrating premise one before you spin off on just assuming it's true... but then, we all know you can't.