It is not a sound argument, in fact it is a well known fallacy formally referred to as argumentum ad hominem.

If we started accepting such arguments the very first thing you would have to discard is Christianity itself. After all, this religion was founded by people who had invested their whole lives into following someone they thought was the messiah but whose death shattered their world view. Can you imagine anyone more desperate to grasp at straws in an attempt to reconcile the reality of what happened with the fiction of what they thought was going to happen?