The suicide note said people are dying young because of fossil fuels. So...
That's one of the most uninformed statements, but it's not too surprising, given the state of mind you must be in to immolate yourself as a form of protest.
People are living longer because of fossil fuels. Without fossil fuels, we'd never have the industrial revolution, which means we'd have a life expectancy somewhere around 50-60, provided you survive childhood. Taking into account childhood deaths, it'll be in the 30s.
(And that's the absolute most basic analysis. We can go into how much our lifespan has been increased by the use of fossil fuels, but I think the "no industrial revolution" is rather large enough.)