The point is that legislation like SOPA exists because corporate lobbyists introduced it. By punishing the companies that support the bill, we undermine the bill, and discourage others to adopt our side of the issue. Laws like SOPA are driven by money. When representative democracy fails to represent your view, voting with your wallet is a perfectly valid means of challenging policy.
Thing is, money talks. If/when supporters realize it's going to cost them -- both in money and in publicity -- things will start to change.
I also favor "striking while the iron is hot". If the tech community can take the current attention and focus and use it set off the metaphorical small nuclear device, supporters may be sufficiently burned to at least hesitate for a useful period of time before trying this again.
If they don't listen to your vote in the booth, make them listen to the vote of your wallet. And your blog (woof!).
At best, it will probably turn out like the issue at Whole Foods, formerly as seen as a very left-wing-friendly food store. The CEO gave a right-wing statement on some social policy legislation and got excoriated for his view. Eventually, after enough flaming, he backed down on the statement, but his views didn't change, just the official company line.
Call it cynicism or whatever, but I don't think Bob Parsons is capable of a real change of heart on this matter unless it seriously affects his pocketbook, and even then, he would be a wolf in sheep's clothing.