Does anyone else think this is wrong or am I crazy?

My bestfriend and brother-in-law live in a double with us that my uncle owns. They changed the locks on their inside doors and didn't ask my uncle. My husband and I told them they should ask first my uncle first before doing stuff like that because thats what my uncle likes. They acted like we were crazy and said I'm sure he won't care and we'll change them back when we leave. We said thats fine it's just the principle of the matter. You should ask first and then my best friend's grandpa chimes in when you rent it just like you own the place and he can't come in their house without their permission. My uncle would never do that anyway. What's your opinion?