The Petaluma slaughterhouse under new ownership by Marin Sun Farms’ CEO David Evans launched into a quick reopening this week under a cloud of skepticism from local ranchers and an animal rights protest.

“Welcome to 1522 Petaluma Boulevard, the new home of Marin Sun Farms-Petaluma,” Mr. Evans told reporters last month. The facility “is the access to market we all desperately need to continue together in transforming the food system… Marin Sun Farms is no…