Fours are a reactive type, but a withdrawn type as well. A lot of them report that it goes on inside.4's don't even seem reactive to me. Any 4 I know...just gets overwhelmed and I leave the alone. Then they're fine. I can't see a 4 doing those things.
I personally can get weird on folks, but it tends to happen through my sx-first instinct--meaning you don't see it unless you get close to me and do something to trigger the responses. I've been pretty sane in most realms, however.
Anyway, in enneagram terms, "reactive" doesn't necessarily mean getting torqued out. It means having some sort of emotional response (and this might be largely internal for any of the types) to a perceived problem and wanting others to get as excited as you are about it. Reactive types can consequently push for responses, but this doesn't necessarily mean getting "in your face" about it. There are many ways to get a response from someone, and having a big emotional outburst is only ONE way.