It is a German conference. It was started by Germans. It is organized first and foremost by Germans. It happens in Germany.
I find it arrogant to think that presenters should speak a language other than German.
I find it arrogant to think that presenters should speak a language other than German.
There surely us a kind of arrogance that demands Germans speak English, but I don't see anyone in this thread expressing that.
(I won't even begin to talk about the variety of dialects and identities contained within the modern German state, except to say that there is plenty of arrogance to be found there for those who seek it.)