Stereotyping, even for a positive or clinical (scientific) purpose has always been something I try to “handle with care”, which is why I bring it up.
I don’t like being ‘lumped’ without my consent so I apply that same courtesy to others.
I listen to the people of the group to see what collective notions that have about themselves for proper cues.
Example: a common Millennial interest has been powerful historic figures especially Hitler. It’s a pattern I’ve noticed through the years but I kept under my hat until one day I was a part of a conversation where Millennials (men and women) were talking about “What dating was like” as teenagers for them. Some of the women remember having a pink SS uniform or similar costumes in their wardrobes and a lot of the flirting from “back in their day” had a decidedly Nazi motif from when they were boys and girls. There were about 20 who participated, and it struck me that this was, indeed, a possible common feature of that particular generation.
I’d brought it up occasionally prior to that, but only carefully, as it’s not “my generation” but while that small sample is not representative of an entire US generation of people of a particular age range, it was enough confirmation for me to be confident that my prior hypothesis was potentially valid enough to make more comfortable mentions of this generational fascination.
Even there, I try to keep it in mostly positive terms and not as a way to denigrate a generation. I also keep listening and correcting as I go.