Clearly that doesn't mean all protest methods are always justified, and I even said I think that this is over the line given this particular set of circumstances, but I reject the premise that it would always be over the line.
Highly illegal and immoral, destructive and violent, killed some five-digit number of press-ganged soldiers and civilians, met all of its political goals...
But I'm not really seeing the connection here or why it invalidates the Unabomber example.
The long and short of it is - just about any destructive, devious, and murderous form of protest is considered acceptable, as long as you can convince a large enough segment of society that it's end justifies the means.
It's circular logic, of course, but that's all there is to it. There are no involatile, unbreakable taboos when it comes to seeking political ends - you just have a harder time convincing some people that your cause is worthwhile, when you are using more extreme ones. And even if you win, you might still be condemned by history for your methods.
On the scale of extremes of methods, this thread's subject is notable, novel, interesting, but is more on the 'misdemeanour hooliganism' side of that spectrum.
“Every protest ever has had people saying that the disruption to them is over the line”
So which crimes would not be acceptable in a protest? And if people will always complain about the line being crossed, does this mean there can be no line at all?