I must respectfully disagree here. LGBT people are only my brothers and sisters through whatever quirk of fate brought them into existence, and I owe them no more than the rest of humanity. Who I owe are the people who've pursued LBGT rights, whatever their sexual and gender orientations happen to be. I feel little different about whether an opponent of gay marriage is gay or straight, other than the somewhat mild irritation of watching someone cutting their own throat ( that said, I'm not a woman and I have the same feeling about certain "anti-feminist" women I've run across ).
If people change their minds in later life, that's fine; everyone makes mistakes. Until then, I feel no need to look upon them charitably.