Just before the holidays, as many of us here in New York City wanted nothing more than a brief reprieve from politics, our mayor, Bill de Blasio, killed a deer. It was a small, furry, single-antlered, white-tailed buck that had appeared in Harlem. For much of December, the deer became a kind of mascot for the neighborhood, spreading Christmas cheer — until it hopped a fence into a local public-housing project and de Blasio, citing safety issues, sentenced it to death. Although this was an ultimately rational decision, the image of a powerful official euthanizing a lost animal had miserable…