technically he didn't call him a goat fucker, he said calling him a goatfucker is illegal. which it is, wether or not the one being accused of being a goatfucker is a leader of a country or not. it's called "beleidigung" and can be prosecuted under http://dejure.org/gesetze/StGB/185.html as long as the recipient (or his/her commander in millitary or <supervisor> in the church) goes to the authorities and delclares that it should be prosecuted ("strafantrag").
i go dakor with the (currently) most upvoted post it's smart from mutti (merkel) to "allow" it, because of diplomatic relations, when in fact she doesn't have a word to say in that. she can allow or forbid everything she wants, but as she is part of legislature and executive, ?judicative? can do what they have to and don't give a shit what mutti says