Tbh I just consider dumb people dumb regardless of their age

20?

I'd probably say 17... I would say higher, but really - if you don't know what you're talking about, don't talk about it. And we're all still students at the end of the day.

Beyond 20 I'd say. That is the age when it is clear that face slapping never helped.

three, time for those ankle-biters to shape up

People mature differently, I'm still pretty immature at age 31, but if you're mid to late 30's and still haven't figured it out that's pretty damning.

18, that's the official age