1) Assume the user's version is true and lose some (maybe a lot of) faith in SE.
2) Assume SE was in the right and the user is misrepresenting events. This is unlikely given the user's reputation.
3) Assume things are somewhere in the middle of the user's version and a version where SE was in the right. This is disappointing though, because it feels like the usership could stand to learn something by understanding what really happened.