"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. What was that tall guy insecure about? Or this one?
Here's another example of what I'm talking about. A user correctly points out how mocking fat women is considered offensive but insulting short men isn't. Someone else immediately jumps into the conversation to gaslight him and make it seem like the issue is on his end: http://archive.is/BvjMg
It's basically a way to silence anyone who dares to question why height discrimination is still so widely accepted, especially in today's politically correct society. Nothing screams insecurity like pointing out double standards, aka using logic. Don't want to be called insecure? Then let us discriminate in peace. This wouldn't be as bad if most people today weren't complete hypocrites who get offended when women are body shamed.