The unjew theory is interesting for sure, but I don't quite buy it. First of all, Scrooge is not a moneylender in the traditional sense reserved for Jews. He's more of a banker or financier, it seems, and there's no implication that his business is not reputable in the mainstream of business and society. He's just a hard boss with a poor social life. Second, Dickens was not notably shy about identifying Jews as such when it was convenient, was he? He certainly didn't seem to have to pussyfoot around Fagin.
While anything is possible, I think it's a stretch to assume that Dickens had any desire or need to encode his tale. Scrooge is, for whatever reason, a miser and a misanthrope, and, for whatever reason, he finds that this life has not served him well. When he muses on its implications, (you can choose hallucination, dream, fiction or true ghostly visitation with little difference in result), he realizes that he'd be far better off to shed that persona and does so to everyone's benefit. If it's popular and well loved, it's partly, I think, because it is so generalized and universal, without addressing any religious or ethnic divisions. The religious aspect of Christmas here is assumed to the degree that it need not be dealt with. It is so comfortably enveloped in its Christian framework that it can get away with being essentially a secular story.
Is there any reason to believe that Dickens couldn't have been more explicit if he'd wished to be? I don't recall Dickens ever being very shy about saying just what he meant, so if this story seems to be about a change of outlook rather than a change of religion, why not take it as such? Perhaps I am wrong, but Dickens seems like one of those authors on whom exegesis is wasted.
e.t.a. I like Gawdzilla's ergot. Scrooge is just the sort of character who would eat bad bread and wash it down with bad water or spoiled beer.