Ad-hominem arguments are demoralizing. Not directly, by making you believe whatever they say about you, but indirectly, by making it clear that whatever you want to communicate is going to be filtered through a pre-existing perception of disdain. They say “I don’t like or respect you, therefore I’m not going to listen to what you have to say or give it any serious consideration. Good luck getting through to me.”
Who would go to the effort of making a heart-felt attempt at communication, given such a barrier?