We are talking about two groups saying mean things over the internet, which are more or less equal.
I'd disagree. There are differences there that can hide rather well. The most important, of course, is credibility.
Let's say I make the following threat, directed toward you: "I'm going to murder you! Murder you to death! I'll kill you with murder!"
You, presumably, will be unaffected. We don't know each other, or anything about one another. You have no reason to believe I have the ability to make good on my promise. I simply can't make a threatening threat that will threaten you in the slightest.
Now, image we're high school classmates. You say to me, over facebook, "After school tomorrow, I'm going to pound you until you piss blood".
That's a far more credible threat, as I know you have the knowledge and opportunity necessary to actualize it.
Now imagine that you're the target of a large movement filled with very angry people and you receive a number of credible threats...