Every large social platform has groups of people who hate each other, even lemmy. They just all have ways to keep only showing people the posts from groups they support (through defederation and only looking at specific communities, or twitter/youtube/tiktok/facebook's algorithms, etc)
I think the comparison with Lemmy is moot, since Lemmy (or the Fediverse as a whole) isn't owned by one centralized entity. Twitter quite literally has a Nazi as its owner. Sure, progressive people still have tools at their disposal to be able to use Twitter, but I think it makes sense to question why we should use such a platform.