Notwehr ist diejenige Verteidigung, die erforderlich ist, einen gegenwärtigen, rechtswidrigen Angriff von sich oder einem anderen abzuwenden.
The German self-defence legislation is actionally pretty good, as it does not require adequacy. You can do whatever it takes to stop an attacker, as long as his attack is enduring and unlawful. This covers attacks on all your legally protected goods, such as health, property and even honor. So, strictly according to the law, if someone would keep insulting you, thus attacking your honor, it would be within your rights to attack that person.
What a judge would say in such extreme cases is obviously a different story.