Grouping by user rather than by content has a major weakness. Grandma can be lovely 99% of the time and a horrible racist the other 1%.
Having been on the 'Net since before the Eternal September, I haven't been able to quite understand this drive to purge "things I don't like" from public forums.
If grandma is really lovely, but has some bad habits from her youth or a different time or something -- then don't mark her post as "racist".
I don't believe, either, that people are incapable of learning. If she spews hateful invective and then doesn't get happy-birthday wishes, she'll learn! Sheesh.
Remember, your K-means Clustering will be public; its easy to see where you stand, and why you got there! If people in your preferred group prefer to not see people spouting the N-word, you might want to consider reforming your habits and beliefs, if you want to remain a functioning part of that group!
The problem is not moderation: it's the belief in a consequence-free existence.
Restore evidence-based reality == restore civilized society.
But, there are a lot of people who don't like that idea.
Most people are like Grandma, just on different topics. The extreme but possible endgame for your system is everyone stuck in clusters of one, because they've banned everyone else for different offences (or those people have banned them).
In real life people take the bad with the good and learn to ignore minor disagreements (and some big ones too, up to a limit). That is a stable system which has worked pretty well for a very long time.
On the internet, there is little of the former (Our monkey brains are not default-wired to treat text we read on a computer with respect and empathy), and none of the latter.
Personally I like some cross-pollination. It can take me by surprise when I'm subjecting to the vagaries of the public.
People tend to protectively double down, and get very defensive, even over very benign topics. Some thrive on that friction, some just would rather leave it alone and drift towards those with similarish outlooks.
People also have a tendency to believe what they want to believe.
I got a load of stick off a friend, because he thought I held a particular political persuasion. Just because I mildly challenged him. Well I'm not even sure as to why he thought the way he did. He just put me in another box/bubble that wasn't his, and lashed out at me. Quite ugly behaviour in my mind. As soon as he realised we were on the same page on the topic, he vaguely apologised for his outburst. To me however, I was left thinking, well what if I hadn't seen eye to eye. Nice guy in the main. Just like racist Grandma.
Anyway I think what I'm trying to say is that I expect differences of opinion. And can accept them (outwardly at least, up and to a point, maybe..). I like a bit of healthy discourse. But the subtleties and lost contexts can be horrible pain points of misunderstanding. Some just can't stand a difference of opinion.
This insane drive to change the meanings of words (eg. every traditionally conservative leaning person is now a Nazi, and everyone proud of their unique cultural heritage is now a Racist, so long as they are also white) is no problem!
A member of a brittle, sensitive, easily-triggered group will quickly find themselves isolated and hearing only the few people who almost exactly match their identical beliefs. And, even those won't last long (just until the first imagined slight or use of the wrong adjective).
This, too, is instructive. Coddling a lack of resilience is not helpful to someone -- but, whatever. Fill your boots! If it works for you, have a blast with your two currently-acceptable friends! ;)
But seriously, the current Kristallnacht purge of social media is the best thing that could happen, in my opinion. It'll force a Cambrian explosion of new platforms that more capably handle differences of belief and tolerance!
This is a strawman, and is generally unhelpful to a good-faith discussion of politics, speech, and moderation.