> Leaders generally don't rule for life in functioning countries, and the mortality of individual Kims has not helped the people of North Korea.

I guess you'd say most people in the world don't live in functioning countries then? China, Russia, much of the middle east and Africa are not democratic and sometimes the death of a dictator is the only way to move them forward. USA and many democracies in the west are also backsliding so maybe soon few people will live in a "functioning country".

Counterpoint on Kim: The death of Stalin or Mao Zedong released a death grip on their respective countries. You can't ignore that getting rid of natural death would make individual centralization of power a worse problem.

>How are these people currently oppressing you, and how would the existence of longevity treatments make that worse?

Just one example: Trump using sanctions to block the ICC from doing it's job (and thus letting people in Gaza die and blocking steps of justice against Israel). The fact is that the centralization of power in modern times into individual hands is already unprecedented. Old people are already ruling the world and they'd do everything to rule it forever.