I liked the way this person was reasoning:

"What we do with another consenting adult is really our business, stay out of my bedroom, thank you. I'm not into BDSM activity, and would have a hard time relating to enjoyment of dishing it out, but others do. Some have a hard time relating to me walking through gender walls as well, but I did. It's not so much understanding the enjoyment, it's appreciating and respecting the right to go there, without slamming the choice from some lofty moral ground."

Copied it from this discussion.