what is wrong with AfD based on their agenda?
For Europe, the fact that they are stuck with their idea of little, puny self-interest of particular countries, without any wider vision for the Union. You can agree with such approach but for the EU, the green revolution, closer cooperation or eventually even the United States of Europe, this would be the end. For Poland, the probability of them disregarding the interest of central Europe and trying to make deals with Russia over our heads is quite high.
As I said, give them some money, honours and power and they will fall in line like everyone else.
Bit an incredibly dangerous one
Not if we do it right. As BB said - it's already been done many times before.