This article from CNN has an interview with the pilot of Williams' helicopter; the pilot largely confirms his story. His helicopter was hit by small arms fire (but not RPG), but Williams (or crew for that matter) was not in a position to observe this. I think this is why the crew's account differs. I've flown in the CH47 a time or two, and you can't really tell what is going on from the back. We hit a power line once in Korea which prompted a forced landing; I could see that the pilot was hotdogging to scare the noobs, but couldn't see well enough to know exactly what happened to cause us to go down.
Fair point, but the damage is done. There is a supposed to be a high standard for accuracy and honesty from a journalist.
And it's hard to sell that he didn't know he wasn't shot down, especially after he had been informed of his inaccuracy multiple times and kept repeating it anyway.