At this point, it would be an all-defiling plague, but I should point out that the purpose, so to speak, of Tumblr was not containment. It was incubation: a horrid culture (in the sense of a E. coli culture) that took elements from elsewhere, such as SomethingAwful's detached irony, melted them together and allowed the worst impulses of modernity to fester. As time went on, it became increasingly putrid, with each drop in that ocean of bile encouraging the fanatical faggotry of every other drop, until the mass exodus popped it like a growing tumor.
Reddit is similar, I feel, since it's just sinking itself lower into a similar abyss, one even more intense than that which Tumblr's exiles sprang from. A flight from Reddit now will be an indomitable blight on the rest of the Internet, but it would still be less damaging than a similar exodus at a later point.
