The actual existence of a historical Jesus has become irrelevant in a context in which christianities have become so woven into not only the Euro-American cultural fabric, but globally. It's not an argument that can be won, even if it can be won intellectually. And it's not the existence of Jesus (or not) that's a problem. It is not even the existence of the traditional churches as such that's the problem. It's all the newer stuff that's coming out primarily from the US, to which other churches have to respond in the competition for adherents, etc.
Get into an argument about the actual historical existence of Jesus and you are just going to unite all christians against you, and remember, in terms of numbers, there are more christians outside Euro-America than in it. What would be the point of that, esp in a society where a majority, whatever their church-going practices, see themselves as christians?
As for the business of Taiwanese -- or Chinese, generally -- and ghosts. Sure, people believe in ghosts, there's a whole lunar month devoted to "hungry ghosts", and all sorts of actions are taken to avert ghosts and, geomancy has seen a resurgence. But -- and I think it is a big but -- there's a huge distance between Chinese beliefs in ghosts and suchlike, and the belief systems of the ultra-right fundamentalists. For one thing, there's a hugely pragmatic side to Chinese belief and practices. Almost like taking out multiple insurance policies. And I don't know about the US, but I don't think you're going to find many cultures/religions where lots of people stop venerating the Moon Goddess after the Apollo landings. There wasn't a big fuss, or anyone making some big announcement. Many people just dropped the practice. Moreover, there's a huge symmetry between the world of the spirits and the world of humans -- they are both populated by a similar range of types and personalities, and have to dealt with in similar ways. Finally, other than perhaps the Greeks (?), I don't think there's another culture where one of the most popular tales -- Journey to the West aka Monkey -- is such a huge take-down of the world of the spirits. None of which is to say that there's not a whole lot of silliness done -- such as sending off the dead, renewed annually for some, with mock money, cars, etc... and now SUVs, computers, mobile phones and pda's; don't know whether the latest camera phones have made it yet, but it's only a matter of time.
kj