People who aren't witty (ie the wannabe marine) can't truly under sarcasm. You've noticed those people who don't understand sarcasm or dry humor, or who try to pull it off and fail horridly.
Thus, it confuses them, and they take offense.
Manwhore is funny. He really doesn't understand these basic concepts.
He's also still completely self-centered, which is the exact opposite of the mindset of a Marine, contrary to his claimed outlook. It's more the outlook of a 7-year-old.