Leaving the room is always a good option, as it's not healthy to let things have a very negative emotional impact. You have to take the general flow of discourse for what it is in anonymous web forums, and, if it's not a personal attack, it's probably healthier to not participate in things generally, a mistake to be hanging in that venue, when simply the conversation is going to cause emotional upheaval. You have to anticipate all, in a more Wild West environment. Find another forum, or move on to doing something else, that restores you to a healthy centeredness.
But there are reasons why one might want to stay in the room. Maybe they don't want to miss out on other conversations that are being had. Or maybe they want to use that room to discuss something else that's semi-related, in which case they can try to move the conversation along. Or maybe they just want to learn how to handle the stress, so they sit there quietly and focus on improving their resistance.
There are just so many variables and I think it's important to measure all the possibilities, their pros, and their cons.