If a site like Reddit is responsible for a user posting a link to pirated content, then the phone company should be held responsible for every phone call that aided a criminal act.
Is it possible we could use SOPA to get the phone company shut down?
Unlikely. But you could be vigilant for any copyright infringement the SOPA supporters are doing on their own websites, and then get the rightholders for that content to ask their sites to be shutdown.