That's a terrible caricature of the truth. Professionalism doesn't exclude being a human being. Read some transcript of, for example, Supreme Court deliberation

That's a terrible caricature of the truth. Professionalism doesn't exclude being a human being. Read some transcript of, for example, Supreme Court deliberations (hardly suspect of being unprofessional), and you'll see plenty of banter/jokes etc. If you read actual examples it's pretty clear what people object to. It's not even that these are actual attempts to flirt or anything like that. Telling someone that you have an erection and concentrate because of her isn't flirting. It's a passive-agressive attempt to demean and hurt the other person.