I’m at my friend’s birthday dinner when an all-too-familiar conversation unfolds. I introduce myself to the man to my left, tell him that I work in the environmental field, and his face freezes in terror. Our handshake goes limp.

“You’re gonna hate me …” he mutters sheepishly, his voice barely audible over the clanging silverware.

I knew what was coming. He regaled me with a laundry list of environmental mistakes from just that day: He’d ordered lunch and it came in plastic containers; he’d eaten meat and he was about...