Parody is not a magic wand that erases all copyright claims. One of the legal criteria judges weigh is the likelihood that the parody will be confused with the original. Corbis would have a pretty easy time demonstrating the likelihood that the fake photo would be confused with a genuine news photo, given the number of people who received and forwarded it in e-mail believing it to be genuine.
Bill Gates’ Corbis and the rest of the Left never shouted over the version of the color legit photo of Kerry and Fonda being altered to also show GWBush in the shot.
It was selective enforcement of copyright. Liberals take care of their own.