A simile/idiom similar in meaning to "one man's trash is another man's treasure" only, in this case, it means that what is funny to one person may be offensive to someone else.
Tom: "Man, I told this hilarious joke last night. Everyone laughed but Bob. He was a douche and said the joke was offensive."
Dick: "Don't worry about it, dude. One man's LOL is another man's WTF?"