I don't have a term for this - maybe "hyperpessimistic-sadistic optimism" or something similar - but the only upside I see is that the fact that these doomsday events will happen, and the mass die-offs will follow, makes it easier to sell a Perpetual War of Systematic Extermination of the Bourgeois on the survivors.

We will, unfortunately, inherit a mostly dead Earth, but when we do, the workers who remain will finally understand that it is actually more moral to kill the owner class by the million than it is to let them live.