Calling a particular remark or behavior moronic seems sometimes necessary; I fail to see how it is helpful to characterize a person as a moron.

Most of the time this type of insult is false to fact: your interlocutors are not, in fact, mentally retarded, they are merely wrong. Sometimes obstinately wrong, sometimes wrong in ways actively harmful to themselves and others; but experience proves beyond doubt that this happens to people of average and higher intelligence.

Calling someone a moron is designed to provoke them, and signal something to other readers; it serves no useful discursive purpose.