When you use character assassination against an entire segment of the population for political gain you are undermining the nation. Betraying it.
I don’t think the deliberate destruction of the fabric of our country is silly. They sure don’t, it’s dead serious to them.
While there'd be some validity if used against the latter to ascribe motive, when used against the former it's more likely to show the mudslinger as simply a fool.
(which, given it's a liberal, would be true a priori ;-)