I'm going to contradict sibling and say "Yes".

It's just a Verein (untranslateable, but let's say 'private association/club') with members.

They can refuse to accept members for any reason, and they can kick out members for the reasons they themselves specify.

Currently this section (§14) reads they can kick out members "that are a danger to the purpose of the association or are harmful to its reputation or interests".

So (read cynically) pretty much any reason.