I would say that "online lynch mob" is not possible. There's a big difference between being consistently and doggedly harassed, and being physically murdered by a vicious mob.
https://en.wikipedia.org/wiki/Lynching
> Lynching is an extrajudicial punishment by an informal group. It is most often used to characterize informal public executions by a mob in order to punish an alleged transgressor, or to intimidate a minority group. It is an extreme form of informal group social control such as charivari, skimmington, riding the rail, and tarring and feathering, but with a drift toward the public spectacle.