Ad Hominem simply means personal attack. It is the argument that someone is wrong because there is something wrong with him/her. This fallacy is essentially the fallacy of attacking the arguer instead of the argument.
Example: This is a paragraph of a blog post by a user named “The answer girl”. She obviously is far from having any answers, because of the following post, which is about the rejection of homosexuality being natural:
“But the proof offered, my dear friends, needs to be towards the unbiased side of the spectrum. This means that those pro-homosexuality and/or LGBT supporting websites shouldn’t be part of your argument, since – in most cases – the information is biased and misleading. A friend of mine told me she was reading a book on this type of research, for example, and the authors were a homosexual couples. One would assume that information might have been mishandled or the research conducted might have been leading (i.e. forced), for example.”
One must be very careful regarding the notion of “bias”. In research method there is indeed a serious case for being biased, but the nature of the research itself is very determining in such cases. As you can see above, our answer girl is not trying to go after any evidence to suggest the results of research done by LGBT supporting websites or books are indeed biased, she is doing the very basic case of Ad Hominem attack: The information is biased because it is given by LGBT supporters.
It does not matter who gives the information, a Nazi may claim racism true, but he or she is not wrong “because” he is a Nazi. If we wish to prove anyone wrong, we need to prove their claims or arguments wrong.
This fallacy could be very tricky at times. In a lot of TV shows we can more or less hear things like “You are a member of party X, obviously you agree with anything that your party says!” Of course, a person’s political party is irrelevant to the truth value of the claims they make, or the structure of their arguments. The following conversation between Rachel Maddow and Nick Gillespie in an episode of “Real Time with Bill Maher”:
“You will always take the side of a Democrat over a Republican,” Gillespie replied.
“No, I won’t,” Maddow shot back. “You don’t even know me.”
“I’ve seen your show,” Gillsepie said.
The first line has nothing to do with the truth value of the claims given in one’s show or made in any other program, aside from the fallacious line of reducing one’s arguments or claims (in this case in their show) to their position or political party.
Thought on Homosexuality. The Answer Girl. 12/1/11. [ http://theanswergirl.tumblr.com/post/8790361207/thoughts-on-homosexuality]
Rachel Maddow, Nick Gillespie Have Intense Argument On ‘Real Time’ (VIDEO). huffingtonpost. 06/23/2012. [http://www.huffingtonpost.com/2012/06/23/rachel-maddow-real-time-nick-gillespie_n_1620826.html]