I know Slate Star Codex already gets a lot of attention here, but Meditations on Moloch [1] helped me to stop being a libertarian. I was already well along the way of abandoning those politics, but that blog post, especially the arguments about multi-polar traps was the final nail in the coffin.

I think the past two years has provided even more evidence that simply letting people act however they want based on self-interest and relying on Nash for good outcomes can even be deadly.

1: https://slatestarcodex.com/2014/07/30/meditations-on-moloch/