Once RBG is replaced and Roberts is no longer the swing vote, I predict he will start voting more conservatively. The blackmail threats will no longer be effective once he is not the deciding vote. So all of these "close" cases will turn into a steady stream of 6-3 victories for the Constitutionalist side - exactly that the Left is terrified of.
Like he killed ObamaCare? There were Freepers that argued that Roberts actually killed it by approving it.