Predicting the rapture doesn't seem any more crazy than predicting anything else that only exists in the minds of people.
Billions of christians are prepared to predict that that they will go to heaven on the day they die, and happy to predict that the rest of us will go to hell. The majority are a little more sensible than Harold, as at least they only put their faith in the predictions that no-one can disprove.
As to the bible references, try to remember that this 'book' has had more editors than a wikipedia page, and could no longer really be said to have an author. There is every chance that the majority of it's authors were just as serious, hungry for attention and possibly even crazier than mr Camping.
So yes - I'd put him in the same camp with all those who claim to be authorities on 'the word' of a fictional being -