John Judis is a socialist who writes for the New Republic. When he wants to do an attack piece, he's savage. This is controlled and contained for him.
It's certainly something one can disagree with or criticize, but it's not especially vicious considering who wrote it.
The idea of pinpointing a politicians supporters as part of a class is sort of beside the point. As you note, it can be used as a snobbish put-down.
More to the point is understanding just what it is in a politician that appeals to voters and just what it is in voters that politicians appeal to. That part of the article may be more worthwhile.
By describing Trump’s supporters the way he did he tells me everything about what he thinks Trump’s appeal is. If that’s what he thinks it’s no wonder he adheres to socialism which is an ideology of non-thinking robotic serfs serving a tyrannical overlord class of law givers. No matter how reasonably he presents it I don’t need to read any further exegesis on his opinion of liberty-minded people drawn from that delusional mindset.