Nobody said "purely." The movements that overthrew the British raj, apartheid in South Africa, and the Jim Crow south were messy. And the work is never over. But assuming that we MUST engage in armed resistance in order to succeed is both factually untrue and not very practical in today's U.S.A.

Violence, and the credible threat of even greater violence, accompanied each of your examples. True, the U.S. is exceptional, and we might be the first time in history where non-violence topples an authoritarian regime. Or, non-violence with an authoritarian could be suicide. I guess we’ll see.