"BULLSHIT!!!" is an offensive vulgarity. It is a vulgar way of saying "that is a lie" or "you lie" as offensively as possible. It is most often used here as a way to skirt the TOU while calling someone a liar, and to bait them.
On the other hand "LMFAO" isn't a vulgarity, and means something as specific and quite different: "get real", or "I know you can't be serious".
Apparently, "that is the way it is Charlie Brown", but I was wondering if there was actually a reason for it.
A casual stroll through the lunatic asylum shows that faith does not prove anything. Friedrich Nietzsche