It's not centralized. It's democratic.
But it isn't democratic. How do you vote? How do you guarantee the vote is fair, accurate, and timely? How do you ensure the people voting are informed? How do you make sure the person who has the ACTUAL POWER to make the changes follows the will of "the people".
Even if it was perfectly democratic, humans fail. The federal reserve is a great idea in theory. Money supply SHOULD match economic expansion so that pricing power is always the same. IF the Fed worked in actuality a dollar today would have the same pricing power as 1970s or 1920s or 1800s. In reality it fails. Humans fail. Giving an elite group of humans control of Bitcoin is the day I stop mining forever (or support the alt which doesn't do that).
In the case of Luke's attack, there is no doubt which is the attack chain and which is not. The consensus is unanimous. So if this were bitcoin, we would be check pointing the last good block and moving on with life.
For example say Luke was the one who had the power to write and published the "right chain" patch. Oops. You now just guaranteed the attack chain has superiority.
In case of a threat of a repeat attack, implementation of an algorithm that performs simple spot checks to detect a bogus chain (discussed in other threads, Gavin contributed a few potential criteria), many bogus attack chains could be auto rejected with no human interaction.
This I have no problem with. There are automatic methods which could make the blockchain smarter and more resilient to 51% attack without going down that slippery slope of human manipulation.