Earle's music hasn't been on radio playlists for years. He gets most of his exposure from NPR (which will still play him I'm sure)(@$$holes) and David Letterman (who will stop booking him).
I was (until this) a big Steve Earle fan. I think a lot of his fan base was relatively conservative. Farmers, FREEPERS and vets....none of whom are likely to buy his stuff after this.
He'll get a little bump from this controversy but then fade away for good.