That line seems blurry to me. How do you define both and where is the line? I'm not sure that many angry emotional twitter users contemplate any line, I would assume most just think "I strongly disagree with that person's opinion or actions and I must punish them". I think most people would agree that harassment and doxing are bad, but I also think that most people would think that doing bad things to "bad" people is sometimes ok. Mobs of emotional people are not paragons of morality, bad actions by a few quickly spread and the morality of the mob normalizes to that new worse level.