If someone is being abused in front of you, obviously the sane response is to say "Hey! Enough of that!". Even Ajahn Chah berated his monks sometimes for misbehaving, if he thought they'd listen.

But there are two things to consider.

First, your own motivation. If you're intervening out of compassion for both the victim and the perpetrator, that's ideal. But if you're acting in anger, then you're only marginally improving the situation at best.

Secondly, the extent of your involvement in the context of the nature of the world. There will never be a perfect society. So while we can help, it's not worth dedicating your life to.

I'm sure there were people who dedicated their lives to fighting injustice in pre-histroric societies that nobody no longer knows even existed. And for what?

So what should we do? Purify our own minds and conduct. That's the only thing we can do that can have a significant and long-lasting effect.