Personally, I'd argue that religion of any kind doesn't "belong" in Germany, or anywhere else. However, religion exists, and the majority of the world's people believe in it in one form or another.
There are therefore, in my opinion, only two rational responses. First, outlaw all religion. This has been tried in China, Vietnam, the USSR, Cuba, etc....generally with terribly results (not only failing to eliminate religion, but causing terrible suffering in the attempt). So, while arguable a rational response, it is not terribly practical, and personally I'm opposed to it. Second, allow all of them. There's no room for saying "This religion 'belongs', but this one doesn't."