kurokotetsu said:
I shared a drink of water mouth to mouth
Is this some sort of euphemism or did you literally spit water into someone's mouth? If so, that has to be the most disgusting thing I've read in a week.
OT: Depends if I knew the people or not. If I saw a couple that I knew well really going at it on a bench at the mall or whatever it would probably make me throw up a little in my mouth. If didn't know them I would probably not care all that much as long as I wouldn't have to be near them for long.
I feel like this topic is similar to what Shamus Young covered in this article:
http://www.escapistmagazine.com/articles/view/video-games/columns/experienced-points/11943-Why-is-a-Bare-Breast-More-Offensive-Than-a-Severed-Arm
In particular this quote seems to fit:
George Carlin once said, "Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?" The same idea applies here. We all seem to think that everyone more conservative than us is a prude, and everyone less conservative is some kind of sex-crazed hedonist. We tend to classify things as offensive if they're shocking or go beyond the norms we're used to, and these norms are generally shaped by stuff like tradition, climate, and viewing habits.