I like to follow up by asking if the thing they're complaining about describes themselves
Eg. So are you a recent immigrant? So do use you recreational drugs regularly? Are you currently banned from social media due to your age?
Then follow that up with "oh I just assumed, because you're the only person I've ever met who talks constantly about this one thing. Obviously you wouldn't be talking about it that much if you weren't going through it first hand".
This works great because people do grievance BS to try to distance themselves from whatever group they're talking about. Anything that imples they're actually making themselves look closer to the group they hate by hating sends them spinning.