[1] https://www.nlrb.gov/resources/national-labor-relations-act
Using that kind of sensational language to describe something routine makes it hard to take you seriously.
Medical doctors, university professors, and librarians are largely unionized. Do you believe the American Association of University Professors threatens colleges with arson when negotiations aren't going the way they want them to?
History?
> Medical doctors, university professors, and librarians are largely unionized.
Doctors aren't exactly a union - they're a licensing body. That distinction matters rather a lot for this discussion. (No licensing body has ever threatened, let alone carried out, violence to prevent outsiders from taking jobs, to the best of my knowledge, but unions have done so regularly. On the other hand, licensing bodies have the authority of the state behind them, so maybe it's just somebody else who does the violence...)
You're right that the AMA has never threatened or carried out violence, but then again, neither have any professional unions I've ever heard of.
For the record, I've spent ~6 years in unionized workplaces and never heard the school teachers, university professors, or government employees who had union cards conspire to commit violence. I would recommend reading about professional unions before decided that they are violent based on "History?".