Unfortunately you are right, what Bill does best is retaliate. If you worked closely with him you will know you can't have a straight talk with Bill unless you are going to tell him how great he is. This is actually how he eventually got managed out. So many people start complaining thru other channels that a different image of Bill started to emerge. It was just a matter of time from that point on. You can protect a false image only for so long. He's lost his credibility and support inside MS at the point it was embarrassing to watch him in the hallway.
If you want to present the truth you need to present both sides of the story.
You can dismiss anonymous comments, but you need to know you won’t be able to hear the other side of the story other way. Bill will use any method to hurt whoever brings up the painful truth.