Gross. But (most) Europeans don't really understand freedom, so this shouldn't surprise anybody.
Actually I find it normal that Erdogan can sue Boehmermann for defamation. Let the courts decide whether what Boehmermann said on the show is libellous or not.
What I find problematic is that there is an extra paragraph (the so-called Shah paragraph) for defamation of a foreign head of state, that allows for higher sentences. Legal prosecution according to this paragraph requires the agreement of the government. (Legal prosecution according to the ordinary defamation paragraph does not require this.) I find this paragraph antiquated, why should foreign heads of state have privilegues? The government should not have agreed to legal prosecution according to the Shah paragraph. Erdogan has already requested legal prosecution according to the normal paragraph, that should be enough.
Invoking bestiality and paedophilia is very clearly unacceptable, regardless of whether it's directed towards a citizen or foreign dignitary. It's filth and slander, and the man should be prosecuted, as he will be. No police protection is deserved.
If you would have watched or read what Boehmerman said before and after the poem, he actually said something like "You must not say 'Erdogan is a pedophile, zoophile, etc.'". Of course you might say that this was a cheap trick so that Boehmermann could insult Erdogan and maybe it was.
Apart from that I have often read things like "That's not anymore satire, that's only filth and slander of the lowest immaginable level". Yes, of course, otherwise it would not have served its purpose. Boehmermann wanted to say something like "You feel insulted by the fact-based, satirical Extra3 song? I'll show you what a real insult is!" The way he did it was the best way to get his message heard.
Finally I find that many Germans when judging satire exhibit a very "conservative" concept of
art, that ignores the fact that the artist interacts with his environment. Art doesn't take place in an empty space. It may provoke people. It may provoke reactions. It may provoke further developments, some of them calculated, some unpredicted. By this the work of art gets a higher relevance, the provoked developments become a part of the work, or the other way round, the work becomes only the first piece in a greater work.