<human>: Can you succinctly summarize the text in 1-3 sentences?

So a guy I know has been with his girlfriend for 4+ years. He says he loves her but has been extremely dishonest with her. Over the duration of their relationship he's cheated on her multiple times with multiple girls (bunch of random hookups + at least an additional girlfriend or two). He's had girlfriends and relationship arguments with girls who aren't even the 'apple of his eye'.

So due to reasons that do not need to be disclosed he really pissed me the fuck off. Something avoidable on his part and to make it worse he's rubbing it in on how much of a dick he's been. Nothing would feel better than to just send her an Facebook message and watch the fallout from here a weeks before he's deployed into the Marines.

/r/relationships, why shouldn't I do this? This guy is a really dick and asshole and nothing would feel better than to stop him in his tracks and let him know he isn't invincible.
<bot>: Douchey guy cheats on gf. through an extension of his douchiness really pissed me off and now I want reveal the whole thing to the victim.