edit: could who ever down voted post a counter argument? Do you have some reason to believe that SOPA proponents would not make that argument?
And anyone who's heard of SOPA already except a industry/congressman is probably against SOPA, and anyone who hasn't heard of SOPA aside from the Google blackout would be unlikely to hear the suspect Google motive news.
So, Con: People who are already Pro-SOPA have one little complaint to add to their little list Pro: The entire internet population becomes aware of SOPA and realizes that sh*t is real.
I didn't vote you down, but here's your counter argument.
1. Suggesting that blacking out google would not be effective is naive. It would be very effective.
2. While it would be straightforward for to make an argument that mp3.com, grooveshark, and piratebay.org have suspect motives - I don't think the majority of people think "Piracy" when they think "Google" - they think "Search."
They want it to pass without being noticed because they can't sugar-coat this one for the American public.