The no true Scotsman fallacy is an effort to dismiss an opponent’s stance by claiming that the opposition isn’t providing a relevant counter-argument. It can be done by asserting that you know everything about the situation, and that any counter evidence is just an anomaly, rather than useful proof.

The name of the fallacy itself is a clue to how it could be used — that only ‘true’ Scotsman would behave in certain ways, and that ‘no true Scotsman’ would then behave in the way that is being suggested.

One example could be that there’s a claim that the students from Jones College will pass the exam, and no Jones-educated student could fail it. If one did, then by saying that they’re not really a Jones-educated student, would be a way of using the fallacy to dismiss their failure.