When I want the real truth I come to the milescity.com
I watch NBC Nightly News for about 10 minutes a month so no matter what happens it's not a huge impact for me. I find Williams' on-the-air tone and demeanor to be tolerable. If you disagree with his politics (i.e. "He's too liberal.") that may have as much to do with his boss(es) as him.
If you put yourself in his shoes, probably pretty scared flying around wartime Iraq in a helicopter ("those things get shot down all the time!") with discussion of other aircraft taking enemy fire, and landing in a place other than you were supposed to where you saw a helicopter with damage from (you were told) an RPG, and so forth... he may not readily know if that damaged helicopter was in his original group of helicopters or a different group. He may not have been privy to the radio communications that the soldiers heard. He may have been seated in a center rear seat where visibility of things going on around the helicopter is poor.
I don't know in what context he originally told the story but I could see how he could unknowingly misstate what really happened, then have the public glom onto the slightly incorrect story ("Brian Williams' helicopter was shot down!") at which point he is boxed in to either playing along or having to correct himself and let everyone down ("Brian Williams' helicopter wasn't really shot down, but landed next to one that nearly was!"). It's not until everyone starts calling him a liar and demanding his head that he fully appreciates the consequences of not speaking up.
That's my take on it.