This is one of those maybe-stating-the-obvious things, but I've noticed that people are using the word "racism" to mean two different things. Some use it in the narrow sense of "racial prejudice". A person is racist, or is a racist, because they believe that one race (usually theirs) is better or more worthy than another. Others use it in the wider sense of the edifice of racial inequality, the forest made of individual prejudice-trees, the dynamics that harm people because of what "race" society assigns to them.
I've been thinking about a useful categorization of what online forums are for: discussion, support or action.
In a discussion forum, you try to figure out things about the world: ideas, problems, etc. For example, you might discuss whether squirrels are stealing everyone's TV remotes.
In a support forum, there is a community for providing emotional and practical support for coping with some problem. Say your TV remote keeps on vanishing, and having to buy new ones constantly is a pain.
Finally, in an action forum you seek to solve a problem. It might provide advice on pest control or squirrel repellent you can spray on your remote.
All of these types of forum are useful, but they have different standards of interaction. Lots of shouting arises when people disagree about what kind of forum they're in. Going into a support forum and arguing about whether remotes are really going missing, going into a discussion forum and accusing people of being awful for considering if people are simply misplacing their remotes, going into an action forum and wanting to argue fundamentals, etc.