Seems to me there have been a lot more left wing extremists committing violence than right wing, going back to Leon Czolgolz.
True. The impartial conversation would be either "Right Wing Versus Left Wing Attacks" or "Islamic Versus Christian Attacks."
I am only aware of a few deaths from specifically Christian terrorist attacks in the past few decades (as opposed to people who expressly shouted "Allahu Ackbar!" before opening fire).
However, including cop killers, environmentalists, anarchists, Ted Kaczynski, etc. I am aware of many more people who have killed for left-wing causes, than the KKK whack-jobs we are constantly warned about.
And then, of course, there is Tim McVeigh...