What the hell, I’ll give it a shot:
Ace, it is possible to have a discussion on a sensitive topic without being rude or mean. This does not imply that one must always say nice things no matter what. It means that considerate adults work to avoid being unnecessarily insulting or cruel. It’s called tact.
For example, it is possible to have a discussion on the problem of obesity in America, without saying (e.g.): “And when I met Doper X at a Dopefest, it was pretty clear she had done all the things we’ve talked about: wearing vertical stripes, getting a flattering haircut, toning up at the gym. And yet, I could still tell immediately that she was really fat, and had a huge ass. So these things aren’t solutions to the problem.”
A non-asshole is able to express the same sentiment without saying something so directly offensive. It’s called tact. (I repeat myself as it’s clearly a concept with which you are utterly unfamiliar.)
These are just the normal rules for being a considerate human being. This has nothing to do with being online, except that anonymity gives people like you the freedom to act like assholes without consequence.