Ad hominem

To argue against someone's point ad hominem is to argue against it by attacking the arguer and not the argument. It is a familiar tactic pulled by a weak opponent and, to be fair, by pretty much anyone when the debate gets a bit heated. For example:

Bill (aged 18): It is not fair to charge students high tuition fees because society benefits from being better-educated and high tuition fees could put off poorer but intellectually able students whose benefits to society could only be realised by a university education.

Ben: (aged 40): You are, I think, rather too young to understand the economic realities.

However, too often, the charged of ad hominem! is used inappropriately simply to dismiss someone's argument. This little article explains what the ad hominem fallacy is in more detail.