Does one have to be an iconoclast or revolutionary these days to be validly left? I consider myself to be left of center, and very much in favor of progressive policies.
However I find myself being disagreed with quite often, mostly for not advocating or cheering violence, "by any means possible" change, or revolutionary tactics. It would seem that I'm not viewed as authentically holding my view unless I advocate extreme, violent, or radical action to accomplish it.
Those seem like two different things to me.
Edit: TO COMMUNISTS,ANARCHISTS, OR ANYONE ELSE CALLING FOR THE OVERTHROW OF SOCIETY
I'm a peaceful person, I try to live by the ethos of causing as little suffering around me as possible. So to me a violent uprising in the name of making a better society is a lot like fighting war in the name of peace: it doesn't make a lot of sense.
When you see a leftist advocating for violence, I think it's usually one of three things: someone who is disenfranchised with their perception of what they can do as a an individual to better society, someone who actively wishes to be violent and will attach themselves to whatever cause justifies that violence, or someone on the internet stirring up trouble.
I'm not aware of a violent leftist uprising which didn't devolve to authoritarianism. Even the French revolution which is often upheld as being a turning point for democracies around the world devolved into a reign of terror and gave us Napoleon.