Some laws are unjust. This is one of them. We have plenty of unjust laws of our own. Of course, each country is sovereignly responsible for its laws, good and bad.
The Holocaust and anyone of such prominence that expresses the denial of such mass killings of Jews and/or that it ever happened; and who also reaches a mass world audience of teachings in this denial of historical fact; is feeding into future Holocausts by present and future dictators and should be treated as the German law has written. A monetary fine is but a small slap on the wrist for the seed of terrorism it feeds into by this Bishop's denial.
In case you were unaware, there is a reason for Germany’s law against denying the holocaust.