Pity the celebrity hounds at People for the Ethical Treatment of Animals (PETA): Their pet animal-rights celebs don’t seem to be very well trained. Recently we told you how: PETA favorite Reese Witherspoon believes that “everything’s better with bacon“; one of PETA’s “vegetarian” rappers understands that “meat ain’t murder, it’s what’s for dinner!“; and how legendary hip-hop promoter Russell Simmons, long loved by PETA, eats fish (“Nobody’s perfect“).

Add another name to that litany. He may not be as well-known, but he wrote the book on animal liberation — literally. In 1975 Peter Singer published Animal Liberation, the book that inspired the creation of PETA in 1980. Singer has received his fair share of criticism for his unsavory views, including his belief that it’s permissible to kill newborn children. In a recent interview with Mother Jones magazine, however, Singer disclosed that he’s perfectly fine with occasionally enjoying animal products: “I don’t go to the supermarket and buy non-vegan stuff for myself. But when I’m traveling or going to other people’s places I will be quite happy to eat vegetarian rather than vegan.” While Singer doesn’t define “vegetarian” clearly, the major difference between vegetarianism and veganism is that the former permits use of non-meat animal products, like eggs or milk.

Most amusingly, animal liberationist Singer finds strict veganism strictly optional if it’s a special occasion: “I know some people who are vegan in their homes but if they’re going out to a fancy restaurant, they allow themselves the luxury of not being vegan that evening. I don’t see anything really wrong with that.” PETA, the organization founded on inspiration from Singer’s writings, holds as its mission statement that “animals are not ours to eat, wear, experiment on, or use for entertainment.” We guess Singer would have to add: “… unless you’re eating a really expensive omelet.”