I've got a friend like that. He just doesn't think he's doing anything wrong when it comes to stuff like that. He'll just be surprised and confused if I were to confront him but he's still trust worthy just.. different. I'd be pissed if someone did that, I like my privacy kept private and I don't like when people enter my spaces without my consent. I'd talk to him, just tell him it's not cool. If he does it again then I'd start question things like repsect and trust but hey, you know him best. Use your judgement.