"You wouldn't believe how insecure a lot of short people are. Mention height anywhere and they come out of the woodwork to enlighten you about heightism. Check out /r/short if any doubts remain."
Of course, when people say "mention height," they usually mean "insult short men." Either way, people hate information when it's remotely negative. Then you have all the short Uncle Toms hoping for a pat on the head for not complaining. Discussions about height are only legitimate when a tall guy starts them.
Bonus: a photo I captured of a secure short man in the wild.