Kereedria suggests that healers are more aggressive. Something about throwing out heals. Nonsense. That's not aggressive.
No, healers are rude. Body language matters. What makes healers rude?
They lack any sort of subtlety. They cannot motion in a direction. They cannot look over there and you follow their eyes. No. Instead they yell, out of nowhere, to go, pull, attack. Or they seem to shove you with a prayer of mending or sacred shield, as if they are kicking you out of an apartment and throwing your socks out the window.
It's not that they are bad people. But they are stuck in the back and easily squish.
In contrast a tank can move. He can ease over this way or face over there or target that. Presumably the healers are targeting the tank and possibly the DPS as well. A tank doesn't just look at a mob. He looks and points and says "see that over there?" He has body language.
He can gesture and hint and make eye contact or not.
Imagine someone with no facial expression, no hand gestures, no pointing or looking, and imagine them trying to explicitly state everything. We don't like frowns much or when people back away when we attempt to converse with them, but imagine instead hearing "I am unhappy to see you and do not wish for you to come much closer." I'm sure you'd back away. That's a healer, the talker, the rude and more than slightly uncomfortable to be around one.
Meanwhile DPS are Harpo Marx talking through a bicycle horn and impromptu harp solos while running around doing god knows what, without a word.