How we change what others think, feel, believe and do
Get others to do as you wish through attacking the person rather than using a more reasoned argument about the required action.
Personal attack may include challenges that question their intelligence, values, integrity, motivations, decisions and so on. Their historical successes may be challenged as may their social or professional position. Attacks may even be about sensitive topics such as nationality, sexuality or religion.
If you can wind up their emotions, you may take further control of the situation, providing logical-sounding arguments that are more likely to be accepted than when they are thinking more rationally. Although they may contain fallacies, it is less likely these will be noticed or challenged.
A personal attack can be relatively gentle, for example by suggesting that their ideas are not very good (even if they are). It may also be vicious and wounding, suggesting uncorrectable personality defects.
That's rather an unoriginal idea. Can you come up with something better than that?
You stupid fool. You can't even get that right. No wonder you don't have any real friends.
You always do that. It's because you don't ever listen, of course.
A personal attack put the attacker in the position of judge and jury, and the other person as an obviously guilty defendant. It can seem like a one-person kangaroo court where the attacked person has no right to argue their case.
Despite the obvious social transgression of personal attacks they are surprisingly common. This is typically because (a) they often work (at least to an acceptable degree in the short term), and (b) the attacking person lacks skills to persuade more subtly.
Attacks arouse emotions, and when emotions are high the ability to think rationally is diminished. This gives the cool attacker a further advantage where they may be able to logically dismiss any half-considered responses.
The personal attack often provokes a Fight-or-Flight reaction where the attacked person either fights back or gives in. They are less likely to fight back if they think they will lose, which is why the initial attack may be particularly aggressive in order to dissuade a fight.
A personal attack in a social setting when others are present creates a complex dilemma for the attacked person. If they fight back, they may also be seen to break social values of polite non-aggression. If they win, they may be seen as using their power to harm someone more vulnerable. Yet if they concede or do not respond, they may be seen as weak and so lose status. The attacker also benefits as their aggression reminds bystanders that they are not to be trifled with.