An abusive ad hominem is often dubbed a "red herring." This is because of its tendency to distract an individual from the topic by forcing him to defend himself. Such attacks can be based on things like personal appearance. This is then twisted and used as alleged proof to counter someone's argument. Another variation is called "needling," which is a personal attack without even addressing the argument at hand.
A circumstantial ad hominem exploits another person's situation in order to counter his claims. These circumstances are irrelevant and using them in an argument once again indicates poor integrity. Such an attack often begins with "Of course you would say that," followed by some sort of comment about what the opponent stands to gain. For example, a person might argue that smoking is not that dangerous. A response would be, "Of course you think that. You are a smoker, so you are in denial." "Poisoning the well" is another type of circumstancial ad hominem, this time laid out before the opponent even gets a chance to make an argument. Much like a circumstancial ad hominem, poisoning the well involves attacking a certain characteristic, but with a more general statement. For example, a woman might argue that men have no right to argue for or against abortion. Her reasoning could be that men will never be in a position where they are faced with terminating a pregnancy. Like all arguments, however, the debate must be won based on facts.
The "tu quoque" fallacy is the idea that "two wrongs make a right." This argument is seen frequently among children who argue that they can do something because one of their peers did it. For example, someone may argue, "Well, my brother does drugs, so why can't I?" While this may seem like an argument, it does nothing to justify the stance that drugs are harmless.
Guilt by association is another variant of ad hominem. Rather than attacking the individual, it categorizes him with an undesirable group. The aim is to make the stated position seem immoral while destroying the credibility of the argument. For instance, a person could say that, "Mr. Smith favors universal health care, so he is a communist, like Stalin." Another example would be, "Vegetarians are all just hippies."