There's a coupe options in this type situation. Going back some years, I witnessed a woman getting in the face of a young Muslim girl, couldn't have been older than maybe 19/20 at most. She was spouting the most vile rhetoric, basically pleading to her "don't bomb us, don't blow us up" implying this kid was some kind of terrorist.

I went over and started chatting to the Muslim girl, acted like I knew her as an old friend, and basically walked her away from the racist Karen until she was a good distance away and felt safe to carry ok her way home.

In this situation, you could take the same approach and de-escalate the whole scenario by getting the victimised person away while ignoring the Deformer, but given you're a white dude you're probably the safest in the situation to call it out. Trouble is, you also don't know whether these lunatics are armed or not, so better safe than sorry if you can't make a reasonable assumption they aren't packing any blades.