Oh sure, that's easy to do. You take the Hillside Dairy case. In that case you had a dissent written by Scalia and a dissent written by Thomas. There--it's like looking at an eighth-grade dissertation compared to somebody who just graduated from Harvard.
Scalia's is well reasoned. He doesn't want to turn stare decisis precedent on its head. That's what Thomas wants to do. So yes, I think he has written a very poor opinion there and he's written other opinions that are not very good.
As Taranto notes, the case Reid cites doesn't even have a Scalia dissent, so Reid's answer says something about Reid's poor reading, but nothing about Thomas's writing compared to Scalia's. Maybe he meant to compare Thomas's dissent to Stevens's long majority opinion. Well, "Scalia" and "Stevens" do both start with an "S," and maybe someone who
It's certainly true that Thomas's position on the negative (or "dormant") commerce clause would overturn a lot of precedent. Reid and other Thomas opponents really are worried that a reconfigured Court might change too many things that people have come to rely on. In fact, as I blogged here, Justice Scalia has been critical of Justice Thomas for not having enough respect for precedent. Of course, if this is the distinction between Thomas and Scalia that Reid is hoping to highlight, he's doing a pathetic job of it by citing an opinion in an area where Scalia has agreed with Thomas.
There is good reason to worry about the changes Thomas would make in this and other areas of constitutional law if he had enough votes, but it doesn't have anything to do with poor writing. Is Reid a racist for impugning Thomas's intelligence? He's an idiot for saying things that make him look like a racist, but I doubt that he is. I think he is resorting to the Thomas-is-too-dumb message because he thinks he can't openly say what he really thinks: that he doesn't like the outcomes in Thomas's opinions. As I've said before, the Senators think they need to oppose a judicial nominee with something other than the will to make the cases come out the way they want. That makes it a lot harder for them to talk about how they are handling nominations, and Senator Reid does not really seem to be up to the delicate maneuvering that will be needed if the Democrats are going to have some measure of power in the coming confirmation processes.