[Tichy]

It's a circular argument form of a very rare type. It actually requires two arguers.

It goes approximately like this:

Arguer A: Your guy's a fascist!
Arguer B: No! Your guy's a fascist!
Repeat.

It is closely related to two other well known argumentative fallacies, the Argument from Say the Same thing Louder, and the Argument from I say X therefore X.