I understand what you're saying, but if the Pope issues an encyclical, he's being guided by the Holy Spirit, whether or not he has the "mental furniture" to understand the gang wars in Long Beach. What's the theoretical millieu employed by the Holy Spirit?
At any rate, as Bill O'Reilly says, I'll let you have the last word. I don't want to beat a dead horse.
He probably is - but not necessarily.
The First Vatican Council's defined doctrinal standard of infallibility does not apply as a blanket covering all phrases in all encyclicals.
And the Holy Ghost generally does not deal in "almosts" and conditionals like "practically nonexistent in current conditions."
Such phraseology inevitably leads to the conclusion that "practically" is not "totally" and that it becomes a prudential judgment.
Everyone needs to take into account this question: "Is it necessary to execute Criminal X?" and apply the reasoning of the encyclical - but there is no hard answer as to what constitutes necessity for every actor in every situation.
The Church teaches that we do have a right to kill in self-defense, but the Church cannot really decide ahead of time in each and every case whether the self-defender could have just wounded the attacker instead given the circumstances in a given particular incident.
A well-formed conscience has to take revealed principles of moral behavior as the basis and measure of one's actions, but must apply them prudentially in each case.