I've had a few events so far where the discussion/feedback part had 1-2 white guys doing longgggg monologues about something unrelated to the main topic. Last time had some stoner guy ranting about the confusing service at airports here (the event was about Gaza). Before that it was some boomer guy trying to explain Madonna to the non-white teens in our group (the event was about trans rights). Sometimes it's just two white guys monologuing back and forth. It's super counter productive and cringe.
I'm just thinking of a hard rule. Like "if you're a white guy, you're welcome, but please try to listen more and keep unrelated monologues to a minimum."
For the record, I am a white dude.
Yeah a lot of the other replies are good ideas, but having what we called a "strong chair" is the only systemic way to handle this. And you need to establish this as a norm over time, so the chair has support from the floor if needed.