Banning an individual, whether permanently or temporarily, is not taken lightly. Several attempts to deescalate a situation are taken well before hand. Some these attempts occur in PM, suggestions, warning, there may be some moving of topics or the outright deletion of egregious/inflammatory posts, or otherwise.
A ban is not and has not been instantaneous for contributing community members. The moderators are generally patient and they do their best to keep things on track. When someone is banned, there has been in nearly all cases, events that had occurred prior to a ban that the community as a whole may or may not be aware of at the time a ban is instituted. So while individuals may agree with a user’s opinion there are most certainly on-going circumstances with some users that continue to push an issue many times too far. History play a large role.