I'll agree that piracy can be damaging, but if you look into some of the wording, SOPA is the equivalent of spraying for termites using napalm. All websites will have to start carefully monitoring everything since they could theoretically get blocked or have their revenue yanked because a user posted some song lyrics or something, and all the added litigation (which will carry no risk for the prosecuting companies, mind you) will likely cost the government tens of millions of dollars. On top of this, downloaders will still be able to easily access pirated material simply by finding the site's IP address, so the affect that SOPA will have on actual piracy will be minimal at best.
If you support any notion of net-neutrality, please contact your local representatives immediately (or if you aren't a U.S. citizen pass this on to people who are) and explain why this bill is important, and why we can't allow it to be rushed through like this.
If you want intelligent, well-reasoned arguments against copyright in general, check out some stuff by Cory Doctorow (who is an advisor in my program at UW, meaning that my degree is cooler than yours).