Stable regimes seem to have less need for oppression than unstable ones. So while I see some risk that mild oppression will be more common with life extension, I find it hard to see how that would increase existential risks.
But why do young men cause wars (assuming they do)? If everyone remains biologically 22 forever, are they psychologically more similar to actual 22 year-olds or to whatever their chronological age is? If younger men are more aggressive due to higher testosterone levels (or whatever) agelessness might actually have the opposite effect, increasing the percentage of the male population which is aggressive.
One of the stronger factors influencing the frequency of wars is the ratio of young men to older men. Life extension would change that ratio to imply fewer wars. See http://earthops.org/immigration/Mesquida_Wiener99.pdf.
Stable regimes seem to have less need for oppression than unstable ones. So while I see some risk that mild oppression will be more common with life extension, I find it hard to see how that would increase existential risks.
Oppression could cause an existential catastrophe if the oppressive regime is never ended.
But why do young men cause wars (assuming they do)? If everyone remains biologically 22 forever, are they psychologically more similar to actual 22 year-olds or to whatever their chronological age is? If younger men are more aggressive due to higher testosterone levels (or whatever) agelessness might actually have the opposite effect, increasing the percentage of the male population which is aggressive.