I'm thinking that the cartoonist was trying to scare us with this image (click to view full size):
Apart from secretly being a Scalia clone, what else do They have on Roberts?
For starters, he's a Catholic. That's suddenly a valid, nonbigoted objection— since some conservatives are trying to get pro-choicers excommunicated, the Left can safely vote against any pro-life Catholic (If you try hard enough, you'll see that B really does follow from A here).
Oh, there's also his association with that sinister cabal-disguised-as-a-debate-club called The Federalist Society: