It's completely justified, awesome and unavoidable it happened in my book.
Being racist is not an "inadequacy" or "mistake".
Certainly not in the context of how Scott Adams chose to air his opinion.
The guy is smart (intellectually, not emotionally) and doubled down on his sweeping allegations, stating that black people are dangerous and cannot be fixed.
No ambiguity in such words, no wiggle room to deflect to a less extreme position.
Anyone keeping in touch with the guy and accepting such bullshit will justifiably be seen as a backer of such a ludicrous opinion and have their own position on racism questioned.
Drawing a line is so important.