what other enforcement mechanism do you suggest? The smart contract method call where Alice murders Bob should not validate unless signed by Bob's private key?
Are you argumenting in good faith that somehow I said that violent crimes should be solved by mathematics?
I said that the legal system works not because of it's complexities or how authoritative the costumes of law enforcement or judges look, but exclusively by the threat of having your liberty taken away from you.
Violent offenders should still be dealt with violence.
But voting? Public policy? Public spending tracking? Economic activity between two private entities? There is no longer need for the threat of a central authority with a monopoly on violence to ensure the proper functioning of those things. Satoshi showed we can have decentralized proof of trust.