"single, pithy, irrefutable reason to hate Trump."
In my mind there was one very clear, important and specific reason.
He lied constantly. Or at least bullshitted. He'd just say any old shit and insist it was true. Like "thousands in New Jersey cheered for the 9/11 attacks".
And... it's not that Scott Alexander doesn't care about truth or truthseeking, right? But somehow lying or bullshitting isn't a big enough deal to him that he would think about that when when he thinks of Trump.