Q: Why would the German Government (a US ally), approve the erection of a statute of 3 people, that almost every Government in the world regards as criminals?

A: Because all 3 of them are all working for the Government as dis-info agents!

Hmmm, thats a narrow view. Germany still respects freedom of speech, art, expression, etc. Also Germany would be foolish to dis-approve as this would most likely make a lot of people upset. Also keep in mind that the former east-German population have a lot of experience with certain things. Being an ally of the US does not automatically mean to be submissive, And turn the population against it's own government, simply because an 'ally' holds a grudge against someone.

You may want to read the little book A Grudge Of Giants by Buckminster Fuller. A very short story that may be helpful to gain some insights when it comes to grudges.