As the title says. Killing a white fox adds a red fox to the menu, and when you're disguised as a fox, foxes still run from you (unless you crouch, of course). Is this intentional? Is this planned to change?

I'm taking a wild guess and thinking its a planned feature at some point. probably being worked on even.

The problem is that theme "types," are handled differently for every entity. For example, FoxEntity has FoxEntity.Type (which is either RED or SNOW, while SlimeEntity has an integer representing size. I don't have a way to abstract this down yet, which is why you can only use whatever the entity defaults to at the moment.

Foxes running from players with a fox identity has been fixed in the latest update.

Redirecting to #55 for the sub-typing issue.