I think it was Joey who once brought this up, but I might be wrong and I might get the exact details right. Hopefully the gist is right though. I think the argument against wood breaks down two ways - one is the apparent 'crudeness' of wood, and the other is the different regional opinions on building techniques (which may well come from an extension of the first point).
Sky scrapers, planes, the Mars rovers, cars (the list goes on) are all made out of metal. We aren't (for the most part) researching new wooden technologies and alloys and stuff, and so the general image of wood is that it's now outdated. Wood is a very viable and useful material with a lot of practical applications, but it is really seen as an older technology. I think this goes some way to explain it. You can tell people all the facts and figures you like, but there will still be people who aren't comfortable with it (see people who are uncomfortable flying, or on trains, or boats etc).
There's also the consideration of the differing markets in the US and Europe (specifically the UK for this example). In the US wood is a much more common building material, with a big proportion of homes and smaller buildings having a predominantly wooden structures. In the UK the proportion is likely the other way, most building here have brick/steel structures. I think this might explain why some people trust wood more than others.
I think it takes parks committing to building wooden coasters to change this perspective. It's quite common to see the new, good wooden coasters having long lines. Guests realise that they offer a different and good ride experience AND they're perfectly safe. It's a complicated issue, someone might be able to cover all the points more succinctly, but I think that might be the general idea.