Am I the only one who thinks this is disrespectful? (please read before answering, this is a sensitive topic)?

It's disrespectful, but they don't realize it because they didn't really know him, if you were in their shoes, it'd be just the same. BTW, RIP means rest in peace, it's a respectful thing to say, that's probably why they put a :). One more thing, it's pretty selfish of you to be saying stuff like "they act like they were best friends" At least they act like they care. You need to stop worrying, he's dead that's that, if you cry, you must be crying for yourself, because there's no reason to be crying for him, he's not in pain, he's not sad, he's not regretful, he's dead and there's nothing to bring him back, get used to it, stop feeling sorry for him, he's in a better place now