It's extreme if you take extreme to mean only focusing on one thing Helvetica, and if you want to know why they're doing it, how will you know if you don't listen to them, or even ask the question?
If I was to imagine the kind of person who'd send a threatening message, they would be extraordinarily angry (not necessarily at the person in the firing line) and very frustrated at not being able to change the way that person thinks.
Maybe they don't have other outlets for their anger/frustration, maybe they do have other outlets and the messages are a continuation of other aggressive behaviour.
Whichever it is, whatever compells them to choose to do this, more people need to be connected to the discussion, but to do that (generic) 'you' have to tailor that discussion to make them want to listen.
Everyone needs to hear and understand the discussion.
But a lot of people just see 'shouty feminist' in an article and switch off.
Like it, don't like it, it's the truth.