Concentrated interests have always had a massive advantage in the legislative arena over diffuse ones. This is probably the central axiom of rent seeking. So how do you stop this sort of behavior? Institute a pogrom against its advocates?
All joking aside, the reason why Lamar Smith hasn't stopped, and won't stop, and why the industries in question will continue attacking until they get their way is that there is essentially NO DOWNSIDE for them for failure. Anti-SOPA interests need to create a downside.
Here is my suggestion. Get a sympathetic Representative and a sympathetic Senator to introduce a veritable RAFT of bills into their houses of Congress. All of them should be contrary to the interests of the copyright industries. Get creative. Some might, for instance, massively expand the definition of parody to include satire. Others might reduce the term of copyrights or the maximum damages you can claim for same. Others might create taxes on the holders of copyrights that increase swiftly as the copyright ages. Still others might just attack the business model of the industry. Essentially tell your bill writing staffers---brainstorm on HOW CAN WE SCREW THIS INDUSTRY GOOD AND HARD, and then write scores of bills to exactly that effect. Don't spend any particular effort on the bills, just get them into the appropriate committee and let them run silent, like submarines.
What you want to do with these bills, besides the 'Sword of Damocles' effect, is to have them ready to go whenever you've got Congress hot and bothered against SOPA, Son of SOPA, or Night of the Living SOPA. Your biggest problem is that it is hard to maintain your mobilization for long, because of the nature of your supporters, and it's not presently feasible to launch a physical pogrom or program against them. So stack the rack with punitive legislation motivated by animus that goes way beyond the 'mere animus' that lawyers sometimes speak of. Then, whenever you parry the strike of a concentrated interest, deliver a club to their teeth with an immediate counter stroke. Your initial counter strikes can be quite moderate---like, say, rolling back recent legislation like the Digital Millennium Copyright Act. But repeated offenses are to be punished more and more aggressively. This is probably the only non-violent way to deal with crony capitalist rent-seekers.