Windmills became only an issue when they started getting into people's view. Personally I like looking at windmills. I consider them an addition to the landscape. More than high houses or smoking chimneys.
There are many things that can make people sick, if they believe in it strongly enough but that doesn't mean the technological progress has to stop. We all don't notice the amount of noise anymore that we are exposed to every day of our lives, especially in tightly populated regions like Germany.
However, on some islands off the coast here cars are forbidden. When you go through the village there at this time of the year, with almost no tourists present, you have the soundscape of a 19th century village. The lack of any background hum or modern day noises is almost deafening, if you know what I mean. You expect it to be that quiet in a desert or in the mountains, far from any infrastructure or settlement but actually experiencing it in a village these days, is a very unique sensation.
I can understand why people get sick with too much noise, I only don't understand why they solely blame power windmills for that. Besides, if the windmills really made us physically ill, then it would also effect animals, as it is proven that animals react to infra sound, for instance when a volcano is about to erupt. But surely though, there have been no reports ever about animals behaving strangely or getting sick in the vicinity of windmills...
