Because he incites an outrage on a daily basis, literally.
I want the leader of the free world to be a decent human being. He should have listened to John Kelly and Sarah Sanders and thanked him for his service. And if he were a REAL man, he would have acknowledged their differences but declared him a patriot and thanked him for his service in spite of that. On camera and not hiding behind his screen.... with a tweet featuring himself.
Events like this just validate the ongoing outrage that we have a petty, small man in the oval office who is the very anti-thesis of the ideals of leadership.