As I said in another thread, racism is a problem in Germany and you can't deny the fact that people in the police force might be racist or biased against certain groups of people. I just think the picture the author paints of the German police force is maybe a bit too harsh, which is why I tried to find a possible explanation. I can absolutely understand his anger though and I do not try to defend the actions of the police here.
Basing my view on the story he outlined I don't think he is too harsh on them - if anything, I admire him for being able to compose such a civilized letter. There are parts of it which are maybe a bit harsh (better-than-canine sniffing abilities - my words), but I wouldn't be able to restrain myself as much as him in a similar situation.