Let every tech industry CEO, CFO and board member call their most senior contact at a supporting firm. Ask them to explain their position, ask them to explain how this _won't_ break DNS, how the precedents set here won't spread to other policy questions or countries. Don't get into balancing one industry or another -- just make them demonstrate a reasonable layperson understanding of how the internet works. The last thing a partner wants is to sound less than informed on the core technologies in their industry of expertise. If nothing else they'll have to go to school on the question.
No doubt many such partners will say they get it but the firm is larger than they are. And that's the point of a law firm, isn't it, you hire one because it provides quick access to expertise on a wide variety of subjects. But if that larger firm doesn't understand the tech business, just how prepared are they to handle technology problems in various corners of the law? Ask the M&A guy, the financing guy, the tax guy, to explain how SOPA won't break DNS.
I don't know where tech billings compare with movie and recording industry. But they aren't small: M&A, financings, patent, etc etc ad nauseum. Beyond that, the network and technology are the core of how business and industry are changing. Maybe these firms stand to gain from SOPA over the next five years. But can they, can the individual partners, afford to misunderstand the technologies that will be driving more and more clients over time? Get on the phone, not to argue, but to make them understand that they are showing an ignorance that could leave them behind.