I wanted to highlight this piece because I think the central message that comes across to me from your post is a very important one. Human relationships are complicated, but in other respects certain elements are remarkably simple. Passing judgement on others - whether it is alleging that non-hetero sexualities are sinful or that those who believe that is the case are bigots - can be hurtful. Opening up a dialogue requires us to move past the hurtful judgements, leave our egos at the door, and listen for a moment.
As simple as that is, it is far easier said than done. We have this asinine saying in our culture that goes "sticks and stones may break my bones, but words will never hurt me." The truth is words leave cumulative scars that never go away in ways that often far exceed what any sticks and stones could do to you. People become bitter and resentful, making that suspension of judgement and putting the ego at the door very difficult. Breaking down that barrier requires learning to respect someone in spite of disagreements. That is best done, perhaps, when that best friend you knew for a long time turns out to be something you didn't expect... and the continuing to love them anyway.
Maybe ask ourselves a question: are you capable of maintaining a positive relationship with someone you regard as a bigot? With someone you regard as a sinner? Learning how to do that is a good starting point, I think.