Are you referring to the email we just read? Because I find nothing at all offensive or inappropriate about it. A forceful dressing down to be sure, but not disrespectful.
I think this line is important:
I'm not polite, and I get upset easily but generally don't hold a grudge
It may look like masochism, but people who work with a "benevolent dictator" know what they are in for. We don't need to be "protected" and if you don't like it, just don't come, the same way I'm not going to play with soccer players because I don't play soccer.
From Dictionary.com, a boss is:
3. a person who makes decisions, exercises authority, dominates, etc.: My grandfather was the boss in his family.
So, for the people who is working on the linux kernel project, Linus is indeed their boss.
If my client was rude and I wasn't ok with him I'd stop responding to him. That's the beauty of freelancing. You don't have to work for people whoose behavior doesn't suit you.
In my opinion swearing doesn't make you a jerk but jerks don't get free pass. They offend some people and get less respect and cooperation from them. That's the social price. No law necessary.
Abuse at workplace is much wider subject. First thing is that there has to be relation of power. Linus has no power over people who he swears at. They can freely choose to never interact with Linus again at any point in time at no loss to themseves or their loved ones. Heck, they can even take all the stuff Linus did, copy it and work on that instead.
No, he doesn't. If your boss or your client would talk to you in that tone you would call it verbal abuse. There is no such thing as a jerk free card, you can always be one but that doesn't mean is excusable.
"I am yet to see him abusing anyone. Verbal abuse mentioned is just swearing in aggressive tone of voice."
This is not the first time that we see this kind of emails from Linus so it is not exactly a new thing. I don't know where are you from that this is considered OK. I am a Venezuelan living in Canada and in both countries this is considered abusive, so it is not only in USA.