Judgment day is not a dud, H. camping, a false prophet, is a dud, as was G. Miller and others before him.
Mr. Camping needs to repent of his sin. He has brought more reproach upon the name of Christ, has hindered the work of the gospel, and has served to leave men complacent in their sin unto the real judgment day.
He does not represent authentic Christianity.
That's a lot to lay on one man. Jesus and his Gospel are quite robust, despite constant attack from then to now. I understand your point, but perhaps the mere fact that he brought the words JUDGMENT DAY out into the square of a godless public is a service of some kind (since his error is quickly corrected via Scripture, as 3boysdad pointed out above).