GameRager: They used to support it because some parts of SOPA would make them immune to any legal actions taken against them by courts if a site they host is found to host infriging content. Now they have backed off due to customer pressure.
Still: they could have planned that many clients would be unhappy, and they should know that SOPA will close the website of many EU based client, notably (because, unlike many copyright holders seems to believe, non US operated website don't have to comply to DMCA request, but rather to their own localized version of it, so until they received the proper form, they'd be SOPA target)
And I think it's safe to guess they'd lose less money in rare stupid trial they'd be sure to win than by losing lots of clients.