Ad hominem
An ad hominem (Latin for "to the man" or "to the person"), short for argumentum ad hominem, means responding to arguments by attacking a person's character and reputation, rather than addressing the content of the person's arguments.
This is a logical fallacy regarding responding to the argument itself, but the method is very effective, since people tend to trust the side with the best reputation, if the issue is complicated or unclear.
The method is extremely common when discussing not politically correct issues, such as race. Those not adhering to political correctness are routinely dismissed as "racists", "Nazis", and so on, and very often without answering their factual arguments.