What I mean by "moral shift" is a rapid change (as in over the course of months rather than decades) in what society considers morally correct and acceptable.

What I mean by "moral shift" is a rapid change (as in over the course of months rather than decades) in what society considers morally correct and acceptable. The dynamics of #metoo and BLM are different in that they are addressing longstanding attitudes and behaviors contributing to oppression or harassment of a minority group (I use the term "minority" very liberally considering that women make up 50% of the population). We've also seen other moral shifts such as with homosexuality, although there was no "punishing wrongdoers" phase following that movement. It's only when a punishing phase gets mixed in that you run the danger of mob justice, because there will likely at the time be either no laws covering the issue, or weakly enforced laws. Without clear leadership on what's right and wrong and the consequences, opportunists take it upon themselves to mete out punishment as they see fit. Sometimes it's for the better, but usually it gets out of hand pretty quickly.