The thing is, public nudity is frowned upon in Germany too, except for special places. So, even ignoring the fact that the place will have refugees living in it and not native Germans, this isn't a good idea for the two to coexist like that.
I just don't really understand why they chose such a location for the shelter. I think the rule should be "first come - first served". The lake was already established as a nudist zone. So regardless of what happens around, no one should be able to cancel the status-quo of the lake without the approval of people who already live there.