So if you can't tell from my avatar, I've definitely seen the show and know of it, haha.
I found out about this show from a friend of mine, who I guess caught on around the beginning of the 4chan craze. I watched a few episodes over last spring before school got too intense, which turned into the entire series. Frankly, I was somewhat surprised that I even accomplished that.
For me (and, to be honest, I think this is true of a lot of the self-professed fans of the show) it's only partially the show itself and a large part about what the Internet has done to it. It's everywhere, obviously, and it can be pure dumb fun to poke around in the fandom, see what kind of art people decide to draw of it, the memes thar arise, etc. I think that's what amuses me so much about it. It's what the Internet has done to it (minus the deep Internet stuff ["Cupcakes"... aaaaghh], but you'll get that with ANY fandom) that makes it amusing.
I certainly don't think anyone should be harping on others because they like it though, or calling names, etc. Let people live their lives and worry about yourself. I know plenty of people too who think that it's like... just odd that it's gained this much attention, but they certainly don't ridicule people for doing so. I think that's where people cross the line.