German law covers this in §32 StGB ("emergency defense"), which includes emergency assistance. If people were reasonably convinced that he was threatening others, they're done & out clear.
P.S.: in German law, it's actually a crime to _not_ render assistance to others in danger - StGB §323c ("failure to render assistance")
German law has extraordinary self-defense statutes, both civil and criminal. The following applies to criminal self-defense:
Any ongoing[1] illegal attack on any legal right may be warded off using force, including insults (that's an attack against personal honor).
The force does not have to be proportional, only necessary (it must not be more severe than another one that would lead to success) and effective (it must have a reasonable expectation of success to start with).
Apart from that there are only minor exceptions (for small children and so on).
[1] "ongoing" is again much wider than you'd think: someone robbing you and running away with the loot? Still ongoing. You following them and striking them down? Still ongoing. Meeting them on the street next day by chance? Not ongoing.
That's for historic reasons, Germany also had a long debate about abortion, and the compromise found was that abortion is illegal, but does not lead to criminal culpability.
According to that, it would be possible to use self-defense for the unborn child against the mother and doctors when she tries to abort.
Obviously, nobody wants burning abortion clinics, and the courts settled on that abortion cannot trigger self-defense.
That's un-principled, and I'm not aware of any legal expert actually justifying it on doctrinal grounds, but it's useful to keep the peace in the debate.
I'm not trying to judge whether whatever anybody did in this specific example (as little as we know) was valid self-defense. I'm just trying to convey some aspects of German law which may be very strange to people from other legal cultures.
For example, whenever I'm reading an article about "the new Texan shoot-first-ask-later law"[1]/stand-your-ground/castle-doctrine I'm very disappointed in the emotional reporting, because it seems so mild and almost pacifist.
That was the very short version, of course. The real legal analysis of self-defense is fascinating, but complex. Just take a look at the table of contents in https://de.wikipedia.org/wiki/Notwehr_(Deutschland)
Interesting, my country has a kind of strange "necessary defence" law - it covers defending something that is protected by lay, not necessarily your own thing - as long as the defence is appropriate.
So you can "defend" someone else, or stop a thief even if they are not threatening you, because you are upholding the law - but you don't get to shoot a thief for example, because that would not be appropriate.
Is this how it works in Germany? I'm kind of curious if we just stolen this from our neighbour.
No, I'm the first person to suggest that (multiple) people believed he was threatening others. Please read carefully :)
It doesn't matter whether he was intending to threaten, or ignorant about the rules, or just stupid. If he leaves the boundary of socially acceptable behaviour (yes this is subjective and established by the community) then he may full well get evicted, and with force if necessary.
On the legal side, a judge or jury would repeat that consideration, and establish whether his behaviour was beyond acceptable for the context he was in. Not by the judge's or jury's social standards, but by trying to understand the situation and determine whether the crowd acted "reasonable." Since there's quite a bunch of people involved in his getting kicked out video, I would wager a guess that there was consensus that his behaviour was inacceptable, and a judge/jury would side with that.
German law doesn't do "I spilled hot Starbucks, now I sue Starbucks for damages". You're expected to have a brain and some level of common sense (or be certified psychologically ill, if you prefer).
Relatedly, the "they should've called the police" argument is legally wrong in Germany too. The allies were pretty pissed off after WW2 and wanted to eliminate the "bystander" excuse for people who watched Jews getting gassed. That's where the "failure to render aid" law comes from. Of course, you're not expected to endanger yourself, but - say, there's an average guy assaulting someone, and you're travelling in a group of 5 reasonably muscular, capable guys... your excuse to not step in is gone.
P.S.: in German law, it's actually a crime to _not_ render assistance to others in danger - StGB §323c ("failure to render assistance")