When I say "fucking zoomer", I mean it in an endearing way. Promise.
If a Gen z kid irritates me, I just link the sounds of dialup modems to them. Much more cathartic.
I mean, I'm vocal to family and friends about stuff like this. I don't see the point in fighting strangers over it and I don't go out looking for strangers to talk to, but I've definitely said stuff to coworkers when I think the joke is going to far, basically a "hey, why don't we just drop this subject" type thing.
Still you're right I'd not really get into it unless they keep doing it.
Edit though the thing I've probably defended the most to my friends (because they aren't assholes who do racists or even really generational complaints like this) has been furry hate bandwagoning. While, like every group of people, there are problematic furries, most of them are just isolated people finding people they can identify with, who can comfort each other. No need to hate em for a fetish/role play if they aren't actually harming anyone or any animals. I'm not even sure I've heard of a self proclaimed furry who actually practiced beastiality instead of just fursonas etc, but rules of the universe say there has to be at least one.