Well it could be argued that the locals were already living in unhelthy conditions.
However, the record of earlier Feldgrau conventions argues that the delegates had "previous". Remember the recriminations over the Belgrade Spring Convention of the year before? Or the Autumn Convention of '39 in Warsaw? The lads were better behaved at the Spring Convention that same year in Prague, but still pretty offensive.
Nope, no tourist department in its right mind would want to host a Feldgrau Convention. That is presumably why they are never asked to.