"That's not the point. The point is this isn't reflective of some general sentiment sweeping Iraq. "
Neither of us are in Iraq. Therefore, this comes down to speculation. It's my feeling that 2% of the population shows a significant trend.
I compare it to letter writing to a company. They speculate for every letter they get, 10 people feel the same way, but didn't bother to write.
For every protester... how many feel the same way but couldn't/wouldn't protest? 5? 6? 10?
Well, if nothing else we have polls as flawed as they may be that show Iraqis generally are favorable to the US presence, though they want it to end sometime soon. And again if this were a general sentiment, then US casualties would be more than 40 a month. We'd be talking about 100s of American dead per month. I think both these things indicate Iraq isn't as seething with anti-Americanism as you want to believe.
By the way, even if you want to use your formulation for out of every 1 letter 10 didn't write, and I have no reason to believe that can reasonably be extrapolated to the Iraqi population and this issue, then we're talking 5 million Iraqis who feel the same way out of 25 million. That's 20% of the population. Significant? I guess. But not a majority sentiment.