I'm quite sensitive to bullying, having often been a victim, online and off.
Part of me wants to agree with you. Richard does "name names" and directly voice an opinion of another person's abilities and a judgement of their actions.
One of the comments in this HN thread reads: "Get off your high horse you fucking moron". That is abusive. Never mind that this comment is in response to someone I happen to disagree with.
On the other hand I did not find the "cutting off his fingers" comment abusive. It comes across an elaborate, possibly overwrought, way of saying "This guy is making me angry". It is OK in my book to give people feedback on how their actions are making you feel. The imagery is violent, the tone is not.
What I do find abusive is the phrase "people like you" which Richard uses in the same comment. So my considered opinion of these comments would be yes, they are somewhat abusive. But I would stop well short of "bullying".
Richard's attacks have a clear object-level target, which is not a person: he is clearly making legitimate (not necessarily true, but legitimate) claims about the TB development process - that it breaks features that worked, that the concerns of some users are being summarily dismissed, and that there is a pattern of these things happening over and over again.
Yes, the tone he uses for saying those things sometimes crosses a line. But on balance, the impression I'm taking away from this dispute is that Richard is being banned not so much for his tone, but more for saying things that are true and that the people wielding the power to censor him are unwilling to hear.
That aspect of the whole mess, the way the power asymmetry plays out, is what I suspect has people coming out in Richard's defense. People with ban buttons should usually err on the side of tolerance.
The success of open source rests on participation, and participation is a two-way street. When you open a bug reporting system, the intended message is "we care about your concerns". Marking a bug as "won't fix" sends the exact opposite message. That makes it, too, a power not to be used lightly: someone wielding that power indiscriminately can easily turn into what I'd not hesitate to call a "bully".
At some point these tensions stopped being about mere civility, and started being about the power politics of open source. At least, that's how it looks to this outside observer.