It’s considered not okay if we replace vegetarian with skin tone.

One is something you were born with and cannot change, and the other is a choice of lifestyle you make.

If you can't see the difference between those two scenarios, that's a huge problem.

The cause or mutability the attribute has nothing to do with the reasonableness of ascribing a certain prior probability to the attribute.

Also, many hundreds of millions of people in the world are born into families that raise them as vegetarians, is that so dissimilar from being born with a certain skin tone?