Do all religions count as a 'predetermined group'? So being against, for example, the enslavement of women at the hands of Islam can land me in jail?

There is a famous example

the images were printed separately in a German newspaper. For the one with the jewish caricature, the paper had to issue an apology.

So yes, if you go by the law any criticism towards Islam should be illegal however in reality it is decided more case by case for the Islam

Germany need to remember that European civilisation was built of the foundation of religious criticism. That's how we left the dark ages.

The German History is full of us refusing christianity and finally defeating its influence on science and state. The song that I embedded is 200 years old and roots back to the German Philosopher and Artists (Dichter und Denker). Those German Philosophers would turn in their graves if they could see the political correctness of today.