I'm not a lawyer. I've only read a lot about SOPA. The problem with SOPA was never that it allowed copyright owners to take down infringing content (well, that was SOME people's problem with it, but not the majority I think). The problem with SOPA was that it allowed said copyright owners to completely ignore due process, and disabled websites in a way that introduced a huge security risk to the rest of the internet. In the Megaupload case, due process was followed, as far as I know. Grand juries were convened, warrants were obtained, etc. etc. The plaintiffs were forced to prove that they had a valid case before action was taken, rather than the "shoot first and let the website owners figure out why they were taken down later, maybe" approach that SOPA entailed.