Ok, sure, there are actual Communist parties. That doesn't mean they're advocating violence, or actually causing real violence to occur.

revcom in particular seems like an ineffective hobby of one guy, based on Wikipedia [1].

Also, skimming around their website, I see calls to protest against fascism, but not calls to violence. [2] contains their "Points of Attention for the Revolution", which ends with We are going for an actual overthrow of this system and a whole better way beyond the destructive, vicious conflicts of today between the people. Because we are serious, at this stage we do not initiate violence and we oppose all violence against the people and among the people

[1] https://en.wikipedia.org/wiki/Revolutionary_Communist_Party,...

[2] http://revcom.us/movement-for-revolution/revolution-clubs/