You're talking about a logical fallacy. That doesn't carry much weight in the court of public opinion, where you're trying to actually convince someone of some

You're talking about a logical fallacy. That doesn't carry much weight in the court of public opinion, where you're trying to actually convince someone of something. If the person doing the arguing is a complete hypocrite, it's pretty normal for others to not even bother listening to the argument. If you want to sway opinions, you need to have an advocate that people will believe.