Killing AI bots doesn't just cripple their ability to be used against us, it cripples our ability to use them for good.

That alone means we shouldn't do it. Add in the huge waste of resources for a battle that will never be won, and it is obvious a better system is needed.

Proof of work can work. Both directly in the interface or indirectly with #bitcoin micropayments. Who cares if it is a bot if it paid and follows the rules?