If for instance you were to look across recent world history you will find many communist ( left ) groups/factions are exceedingly violent toward civilians and account for millions of civilian deaths.[0]
In this country very recently, "...New York City Mayor Bill de Blasio... blamed anarchists and "far-left extremist" groups, including antifa, for inciting and organizing violent riots"[1]
I am not say that violence is not perpetrated by those on the right but your statement is a gross misrepresentation.
[0] https://en.wikipedia.org/wiki/Mass_killings_under_communist_... [1]https://en.wikipedia.org/wiki/Violence_and_controversies_dur...