Because it implies that some contracts will have a greater probability of being "bailed out" if they are backed by more ether.
It may turn out to be a bad thing because it will establish the idea that not all Ethereum contracts are created equal.
And this can lead the system to be more centralized.
Edit: for the record, I don't own use Ethereum or own any ether, so I would also hope that a hard fork doesn't happen to bail out a single contract, but I have no financial incentive on the line.
a) It is being bailed out by referendum, not mandate. Everyone gets a vote, if you don't want to install the patch, don't do it.
b) The funds to bail it out are those stolen by the attacker. Nobody is asking people without DAO tokens to suddenly contribute their ether to restoring the DAO or take debt.
I mean, the contract executed exactly as specified.
If the system was well designed, there would be no way to undo the results. Such a system may never exist, but the fact that ethereum can sometimes change contract results means it isn't living up to its ideals.
Of course, miners not associated with the DAO would never normally consider risking such a thing, but the rapidly falling price of their ether may convince them that it's the safest move.
2) The American people were paid back.
The fork won't be enacted unless a majority of the community agrees to run its code. That's not likely to happen except in extreme cases, like this one.