Of course some could be legitimate and others not. Why does this seem odd? For example, if someone robbed a marijuana dispensary claiming that they were protesting a gasoline tax, I would opine that that was not a legitimate form of protest.
The primary definition of 'legitimate' (linked below) is: according to law; lawful. Isn't it odd that you make such a strong distinction between that and 'legality'?
Interesting. I tend to think of that definition as somewhat archaic, except in specific contexts. However, I will gladly defer to dictionary.com on this matter.
In which case, forming a "human wall" is not a legitimate form of protest, because it prevents people from accessing public property which they have a right to access. If I don't want you to use a park, I do not have the right to stop you from using a park. The same goes for a bike path, a road, whatever.
In an article linked below, Berkeley students form a human wall to prevent only white students access to a bridge leading to campus, forcing many to hop from rock to rock across a stream to cross. In the included video, you may note that police were on scene throughout. While I am not familiar with Cali law, it would seem that restricting freedom of movement as a form of protest is in perfectly legal...
What is legal and what the cops will enforce in a particular situation are two different things. More often than not, if no one is getting hurt, the cops won't stop a protest, even if it happens to be illegal, because it could escalate to a riot and all sorts of bad things can happen. So if you block the streets to whine about your favorite pet cause, the cops will probably let you do it because busting up your protest might lead to greater injury or property damage. However, if you do it often enough, or are enough of a nuisance, and there are few enough of you that they can dispose of you without too much grief, you are breaking the law and are subject to arrest as a result.
Not a trick question, but I think you missed it's point. TBD said you cannot claim self-defense if you are attacked when you have knowingly exposed yourself to a 'threat'. I disagree with this, and a sit-in serves as a good illustration: just because you engage in protest, it does not give others the right to assault you or negate your ability to claim self-defense against an assault.
Got it. You are correct. The "he was asking for it" defense against an assault charge pretty much never works anymore. It might convince a prosecutor or the police to ignore you, but if it gets to court, the assaulter will lose.
Applying this to sit ins, if you assault some sitters, you will lose. On the other hand, if you call the police, and the police arrest the sitters, possibly using violent force against resisting sitters, the sitters will lose.
If there are enough sitters, though, and they aren't causing too much trouble, the police and prosecutors will probably just let you hang out for a while to make your point, as long as no one gets hurt.
Where it gets really tricky is when people have a right to be where they are, but then a fight breaks out. Now exactly who do you blame, and possibly arrest, for the violence? In this case, I have insufficient data to say who ought to be charged. However, if one side has a parade permit, and the other side has masks and pepper spray, I'm going to be immediately suspicious of the masked folks.