Instead of attacking your proposition, your opponent directs his argument against you as a person. Although a person's past record is something one should take into consideration, it should not be one's sole basis for judging an argument. The Ad Hominem attack often takes the form of discounting a proposition by attributing prejudice or bias to its supporters. But what motivates us to believe as we do, say what we say, is one thing. The truth or falsity, validity or invalidity, of what we say is another. It is possible to be prejudiced but right. Another form of Ad Hominem is charging your opponent with the inconsistency of not living up to what he advocates.