I must have missed your accounts of "leftists" rioting, looting and killing each other, and those around them".
As to "modern day events", the robocops, TSA, HSD and so forth are about as "modern day" as one can get. What do the Crusades have to do with it?
As for tea party "folks" being non-violent, you may want to ask the Cliven Bundy groupies about that, as well as the militia men who think we ought to head down to the border and shoot anyone who tries to cross. Extremists of whatever persuasion are fond of inciting others to violence, then innocently asking "who, me?" when it all starts coming down.