I thought one of the main points being brought up is that on the contrary it allows Joe Superminer to progressively drive more and more competitors off the net until he and he along controls all the mining. (Presumably pretending to be more than one mining operation, of course, to keep people from noticing he has become the sole arbiter of the network.)
Did you read the proposal? The decision about how large blocks can be rests with the nodes which relay blocks, not the miners.
If Joe Superminer controls enough of the hashing power and the p2p network to force a change through he could ruin the network today, with or without any change to the protocol.