I had this conversation with my (very conservative) father few years ago when I told him that I support homosexual marriages.
He was like: "I mean them no harm, but are you sure that they made the right choice?"
Well, there were obviously 2 things that needed to be explained. First, if we talk about the sexuality, there's obviously no such thing as a choice. The second thing about sexuality is that there's no right or wrong "choice". Being a homosexual is no right or wrong, just like being a heterosexual is no right or wrong. But it was too much for my dad.
I had the similar conversation with my dad few months ago and he said: "OK, I'm with you, I can support them, but I still can't understand how a man can be attracted to an another man."
Yeah, dad, I'm sure that you can't "understand" how a woman can be attracted to a man, but you don't care about it. Mind your own business then.