Ignore, but if they're a special kind of jerk just point, laugh, mock, and leave. They're so insecure that it will sit inside that empty head and eat like an parasite.

They won't quite know why u mocked them and as 2020 has proven they're deathly afraid of the unknown. Not to mention at their core they just rly crave attention, so when they do not get it they throw tantrums. Remember we are basically dealing with bratty children here.