When you read Fanon, Sartre, Lenin, etc, the violence of leftist praxis is not hidden. For ex., take Sartre: "For in the first days of the revolt you must kill: to shoot down a European is to kill two birds with one stone, to destroy an oppressor and the man he oppresses at the same time: there remain a dead man, and a free man; the survivor, for the first time, feels a national soil under his foot."
For Fanon, decolonization is very clearly a violent phenomenon.