Actually most voters don't literally believe what Wilders is saying. It's just the movement they support because at some points he IS right. BUt hey, if I'm stupid, fine.
Therein lies the greater danger. And you see it in more and more European countries. Haider (gladly with him his party is pretty much going down), Le Pen, the SVP in Switzerland etc.
In Germany as well, though differently. The right-wing parties are attractive in the east and then in some areas, but for historic reasons they remain confined to smaller groups. The left is taking advantage of polemic positions to a greater extent.
The problem with Wilders et al is, they know very well how to talk about these issues. In some countries, such as Germany, also due to legal circumstances. Certain things you are not allowed to say, but word them slightly differently and you are fine (eg. Nazi quotes: You are not allowed to say some of the marching shouts of the SS. But mix two and it's not a historical quote anymore and hence can't be prosecuted, unless it was in another way offensive or denigrading to a minority or society). These parties thus have adopted a language which is very effective. People say, "Finally one dares saying it" and are joining this "movement". It's just mixing very radical positions with more acceptable language. And people think, "Well, sometimes he may be way off, but there is truth to it". Oh well, there is truth to some extent, but there is usually a gross oversimplification of the underlying problems, causes and also solutions. Alongside very popular, but totally unrealistic promises to the base.
And it's concerning that they can amass such a following, and at least as concerning how unable the other parties seem to address these parties. Ignoring doesn't help.