Since many/most DU-grade Progs can't imagine an intelligent, sane, decent person disagreeing with them, this DU-character has pretty much built his conclusion into his definition of "sane".
But I'm totally OK with DU-folk and like Progs refusing to understand and under-estimating Rs and conservatives. They set themselves up very amusing - to us - consternation when those they think idiots beat their candidates and issues. And of such disappointments the most entertaining conspiracy theories are born.