To be fair to AT&T, there's a likelihood that this was all due to a DDOS attack against 4Chan, and that AT&T was just taking defensive measures. Cogent Communications, an ISP, has also reportedly blocked the site, so there may be some trouble in their future as well.
Finally, this comment, by Digg user SpammishKing, helpfully puts the whole story into perspective for us:
"First they came for the pedophiles, and I said nothing, for I was not a pedophile."