If we answer their lies with our lies, observers have to sort their way through a huge muddle. At that point, the contest comes down who can get their message out the best. And showbiz has the money, and the interest, to buy a lot more airtime than the SOPA opponents.
When you're right, you want to move the argument to principles and facts. You don't want the debate muddled, b/c the more people know the likelier they are to agree with you.
(Unless you mean that Youtube really does mean jail? I haven't tracked the less bad parts of the bill so closely.)