Self-defense works when your life is in IMMEDIATE threat
Under most circumstances, yes. But most people are never going to run into a situation where they find out someone is planning to kill them in advance. Approximately a third of all living jews were exterminated in the holocaust, and the only reason it wasn’t all of them is because Hitler had bitten off more than he could chew and was defeated militarily. Jews organizing and killing the people actively trying to exterminate them would have absolutely been justified.