Invariably, in every discussion, they'll trot out this sentence: "You <opponent group name> people always think <notion>".
For example: "You Liberal party voters always support lowering taxes" or somesuch sentence.
I point out that I didn't vote for the Liberal party.
"The Labour party voters are the same!"
I point out I didn't vote for Labour either in the most recent election either.
"Err..."
-- at this point their brain locks up, because they're expecting a tribe-vs-tribe fight and they have no idea what to do when they discover I don't actually belong to their "enemy tribe".