I can't put my finger on it, but there must be a name for this kind of logic. I think pgs arguments have more sustenance than just this, but it still rubs me the wrong way. I'll give an (extreme) example below.

1. Make a statement, calling out some part of the population as "inferior".

2. Note that a trait of belonging to the inferior class would be to disagree with the above statement.

3. Dismiss any criticism of the statement as coming from someone in this inferior class, and therefore being unable to give meaningful arguments.