I think I’ll wait for the police report before jumping to conclusions. But no one deserves to be assaulted.
As for the assault, which I have no doubt happened, we are arguing over the legality of it: People deserve to be assaulted all the time. The person that initiates violence, or otherwise legitimately violates or seriously threatens the physical security of another person deserves to be taught a quick lesson so they can ruminate about personal sovereignty and rights while they heal.
As a general rule, society calls on the strong to protect the weak. Violent people will seek to exploit weaker people. When a violent person errs and unknowingly seeks to exploit a stronger person, it is my opinion that it is the duty of the stronger person in a strong legal and moral position to take the opportunity to perform justice.
Said person doesn't need to know the crimes and transgressions of the aggressor in the past. That the person is now aggressing and violating others rights is enough. If it is the offenders first time, the lesson should hopefully suffice to make it the last. If the aggressor regularly violates the rights of others, it is karmedic justice at a minimum, and true justice if other victims hear about what happened.
TL:DR; it is a moral imperitive to dispense instant karma within the law for those who could not in the past, and cannot in the future.
That's vigilanteism. What you are describing is not legal.
Why didn't Elon's security team call the police if they feared for their lives? It appears the guy from Elon's team got out and filmed the man in the car. He must have thought it wasn't serious enough to warrant a call to the police.
The distinction being that vigilantism happens after the fact, or by people who were not witnesses.
As an example, if someone steals from a business and returns later, its too late to arrest or hold them. But if you perform a citizens arrest at the time of the theft that is legal.
Another classic example is a use of force altercation. All participants should be present from start to finish to avoid legal jeopardy if they wish to intervene. Someone that sees a fight after it started has no idea whose side it is legally permissible to take. Even so, it's very risky to intervene because it's hard to know what's going on in the heat of the moment.
This is why rights must be enforced in the here and now, by those that have standing to do so.
Otherwise, as you say, it's vigilantism.