Not to mention that a decentralized DNS system, which I am not against, will have a tendency to skew towards the illegal/fringe uses where avoidance of the law is paramount.
With all due respect, taking the site's domain name down won't do anything against criminal activity. It just make it harder to track.
Also, it was human elements that force domain name to be taken off the net.
If you have to say "Sorry, we can't do anything about it. It's against the protocol", than you can't take down the domain name or interfere with its operation.