From what my research has pointed out, its more of a poke at someone being Homosexual.
Because the terms "Gey" and "FGGT" are so common in online gaming, casual and hardcore, one would assume that "Butthurt" is more directed at the person taking it "IN DA BUTT".
Such as described in this video.
And because of the blatant avoidance of taking it "in da butt", when one is burned, hurt, or damaged (as one would probably after anal insertion for the first few times), they are then "butthurt".
but thats just my 2cents.
Because the terms "Gey" and "FGGT" are so common in online gaming, casual and hardcore, one would assume that "Butthurt" is more directed at the person taking it "IN DA BUTT".
Such as described in this video.
And because of the blatant avoidance of taking it "in da butt", when one is burned, hurt, or damaged (as one would probably after anal insertion for the first few times), they are then "butthurt".