I use this in all areas, if the goal is communication then you want to convey a message and have a person be receptive. If you insult a person they immediately get defensive and will instinctively reject or try to combat what you're trying to convey to them. It's literally the opposite of what you'd want to be achieving.

The way I see it is insults are for "me," they're self serving in that "I" feel better about myself and feel some sort of justification for insulting you (I personally don't, but I see the appeal.) but if the point is about communication then "I don't matter" it isn't about me it's about the idea.