He's saying that, when person A says something, and person B says that the statement is x-ist, person B intends that to end the conversation. In particular, person B intends that they not have to actually refute person A's statement.
PG's reaction isn't the point at all. The point is the speaker's intent.
If that's how Graham reads such statements, isn't he basically saying "It's heresy to call a statement x-ist" in his presence?
What am I missing, this seems totally hypocritical given the rest of his argument?