[TeMPOraL]

In your first case: it is later revealed that the reason for A's action was B making threats of violence towards their kid and about to realize them.

The problem with third parties passing judgement is that they often lack full context.

[vladTheInhaler]

I completely agree. Outside of these toy examples, there really is no way to know the complete truth. But I don't think we should give up on doing the best we can to recover as much context as possible, and we certainly shouldn't fall into some sort of epistemic learned helplessness and try to make all judgements from a position of zero knowledge.

[Sebb767]

The problem is that anything you allow against the perceived enemy might come back to bite you if you suddenly are perceived to be the enemy. This is especially true when silencing opinions; you're not only taking away their right to speak, you're also taking your right to change your mind.

I fully agree with you that when judging a specific occurrence, the context is really important. Judging completely without context, on the other hand, is good way to know whether the action is something morally acceptable.

In this case, the 'goodness' of the action clearly depends on whether you like the target. So I'd argue that this really is not a good thing in general. It's slightly worse if it hits the 'good guys' and slightly better if it hits the 'bad guys', but it's not good either way.

[lsiebert]

Don't let the perfect be the enemy of the good, as the saying goes.

Any system is going to be imperfect. The question is, is it better than things currently are?