Jesus did not mean that being wealthy was not bad as such. Valuing material things above all so that wealth was no longer the means to an end but an end itself, money had in effect become a god to be worshipped, now that was bad. Note that he says the metaphor to the rich man knowing that he would never give up even a fraction of his wealth, thus setting him up as an example of a man who gathers wealth only for the sake of wealth, not for what it actually brings to him. The man was still not happy with all his wealth, but he would still keep it even if it did not bring him any happiness. Even if he had become happy by becoming a disciple of Jesus, he would not have done it because it would have meant abandoning his wealth.
That being said, I bet that the most ardent and vocal fundamentalists are the most unhappy lot of all. They are so insecure in their faith that they must constantly police one another and point out how bad those other "sinners" are. They want to control others, yet are incapable of controlling themselves, and most importantly, incapable of admitting that. The central theme of Jesus's teachings was that Man is doomed to fail whatever boundaries - be it Mosaic law or secular legislation - he sets himself. Only by accepting that and learning to first forgive one self can one achieve mercy in the eyes of God. Had they truly found peace in Jesus, they would not be so clearly angry and bitter.