Do you really think 95% of the population either already disapproves of the Congress or has been on the internet today and ran into a darkened site and thought about the issue?
HuffPo has a funny take on that, saying that more people approve of "Porn, Polygamy, BP Oil Spill, 'U.S. Going Communist'" than of Congress.
So no it's probably not unreasonable to suppose that somewhat less than half (12/27) of the ~27% people who approve of or are neutral to Congress saw a darkened site and thought about the issue. I know that I got questioned about it at work by the less technical folks.
I'm pretty sure he meant that all of these sites drawing attention to SOPA and PIPA are upsetting Congress. Not that they were trying to get to Reddit.