You're quite incorrect. The state properly has a monopoly on the retaliatory use of force (and none other) under objective laws and legal processes. But self-defense is an emergency, and there is no rational argument to claim that one may not protect oneself, one's family, or one's property against beasts or thugs. On the other hand, if you kill someone in self-defense, you had better be prepared to explain how necessary it was, in the court of law; which is exactly how things work in the USA.

If one is so depraved as to argue that self-defense is unacceptable as such, then one should be prepared to live and die as a slave to the first thug or dictator who walks by one's neighborhood or country.