Yes We Are Hypocritical:

For cringing at the thought of slaughtering dogs and cats for meat but not cows and pigs.

I'd never go vegan and see nothing wrong in principle with eating animal products like cow milk or chicken eggs. However, I do see why slaughtering mammals is morally problematic. I feel less sympathy for fish, fowl and reptiles because they can't feel pain. I'm just kidding about the last part. It's perhaps because they are more distantly related to humans and less intelligent and emotional.

I'm not sure what the term is for someone who just doesn't eat mammals but everything else is fair game; but I could see myself at least trying that diet out purely for ethical reasons.