List the different varieties of animal meat that are sold at a typical grocery. Then ask for each item on that list what is the fraction of the US population that finds it acceptable to eat it. The distribution you will map out is not at all smooth. Most people will either find it acceptable to eat everything on the list or unacceptable to eat anything on the list.
I believe that both mass points are a result of the same phenomenon: the slippery slope. Moral rules are vulnerable to creeping margins and unraveling. If I want to argue that people should not eat meat it is easier to make that argument if I take an absolute stand. Absolute rules are easier to defend then nuanced rules that define some interior boundary (it is ok to eat animals if and only if they have no feelings) because nuanced rules admit cases that are very similar but fall on opposite sides of the boundary (you mean its ok to eat squid but not octopus?)
Likewise, people who insist that it is ok to eat all meat are usually painted into that corner for similar reasons. To accept that it is not ok to eat veal makes your filet mignon vulnerable.
So the slippery slope of moral negotiation pushes us to extremes where we are on firmer footing. All sides lose as a result. Especially those of us who would prefer that fewer animals are eaten. I was reminded of this point by an article from the Atlantic about “semitarianism:” proudly taking the middle ground. Here is an effective passage:
…, recall that even the most fervently ethics-based vegetarianism isn’t really about an ideological purity of all-or-nothing, us-versus-them purism activist groups foster. It’s about reducing animal suffering. Whether one person gives up meat or three people cut out a third, it’s all the same to the cow, and it should be the same to us.
(a little shout-out to Sandeep who is in Tuscany exercising his finnochiana option.)