My MIL just really has no respect for other's people's things. We crate our dog - we've crated any dog we've ever had. She's the type that if I told her to keep the dog in his crate over night or while they were gone (if they were watching him for us) she won't. But she'll be the first to complain he peed on the floor while they were gone. She drives me crazy. And just like you said about people thinking chickens come in red and white - she comes over the first time and sees them and says "I didn't know chickens came in that color or could look like that (referring to my silkies)" But don't worry, I told her I don't know where the silkies came from, they were beamed down here from space. ;-)
My mother used to drive me nuts in that she didn't believe in spaying or neutering the dog. Needless to say the dog would drop a litter every year since many other felt the same way. The pups would get sick and die. We really couldn't afford a dog. I was just a kid. Now I'm a strong advocate of spaying and neutering. I nabbed more than one cat and had it fixed at my expense.
There is little we can do but to try and circumvent their stupidity. I would not leave my animals with anyone who I didn't trust. Including family. Especially family.