I think its a different situation calling out racism etc when you haven't got the advantage.

That's only speaking from a position of privilege. It's a privilege to be able to decide when and how you want to engage. That's not a privilege that POC have.

If I get critically injured, who is feeding my kids?

That's a personal choice for you to make. Me, personally, I've never been assaulted for calling out racist language, so I don't have an overwhelming fear that keeps me paralyzed in a public situation. I do have a legitimate fear of a future determined by white supremacy.

Its better to show solidarity with the victim.

Psh. Ask a POC if they would prefer you cower down and be nice to them after the fact, or if they would prefer you to be side-by-side w/ them in this fight O_o

Don't challenge the bad behaviour, just go sit with the victim qnd ask them about their day etc, make small talk and generally show them that they aren't alone.

I'm not a POC but this just sounds really contrived and condescending. POC don't need wet nurses, they need white people to wake the fuck up!

You don't challenge the bully, you change the dynamic of the situation in a way that removes the power of the bully passively.

I don't even know how to respond to this, it just seems absurd to me.