I'm not sure it's right to call it a meme. More of... a theme. It's not a single idea, phrase, or picture that's spouted over and over, it's a fact that spreads through all things. It spreads through all animes, not just Bleach. It spreads through all boards, not just /a/.
4chan hates things. Compared to everything else we are, nothing about us stands as strong as our hatred.
Oh, sure, we DO like SOME things (though some of us still hate it), but you hear the hatred more. Every nice thing we say, we dig at something else and hate. Every hated thing that fades into obscurity, we replace with something else.
We hate those who are new. We hate those who are old. We hate the idiots. We hate pretentious faggots. We hate the mods. We hate those who break the rules. We hate the world. We hate ourselves.
We are hatred. There is no better way to put it.