I'm going to comment unfavorably on a short colleague's height
Why are you going to say something mean to him?
I'm taller than him and he's such a loser.
It is rude to pick on someone's height.  Especially in a work environment as it looks unprofessional of you to do so.
I don't care what people think of me.
There is nothing wrong in being short. You should not judge people based on their height. In fact you should talk to them to get to know them better.