We are not supposed to waste our times labeling people as a form of gossip. We shouldn’t waste our times talking about people that we all know their wrong manhaj.

But when it comes to warning people who don’t know their true identity, this is permissible and might be obligatory.
I was most likely referring to those who make it a form of entertainment to talk about groups and people and label those who are not with them just as a form of killing time.