I would have a much easier time taking libertarianism seriously if its advocates weren't all in obvious affective death spirals.

This kind of absurdly absolutist statement achieves nothing but display personal animus toward an ideology. It is true that many libertarians are in death spirals, but I know of no political group that does not have large numbers of supporters in Affective Death Spirals. In case you were unaware, this is a universal tendency for idea-based groups.

And politics is the mind-killer, no matter your politics.

I agree with this, though:

Libertarianism does not handle tragedy of the commons scenarios well at all, and that's exactly what most existential risks are.