Innocent people will swear that they're innocent when you falsely accuse them, too.
Usually if there really is no problem, in most cases people will deny it, and rely on the fact that the situation will sort itself out as a misunderstanding. (Yes, that in some situation ends up biting back and all, but it doesn't deny that people will do that). However if they are guilty they will put their full force in denying it and go the extra mile (as in pull personnel files and share them, write articles about it on blogs months after the incident, and so on).