A friend of mine lived in a flat with an indoor communal area shared with three other flats - two upstairs and two downstairs
It clearly said in the lease agreement that the communal areas had to be kept clear for access in case of a fire.
One resident used to leave her baby buggy, scooter etc in the communal area, despite knowing the rules.
This caused a bit of bother but eventually my friend contacted the management company and they went to speak to the other tenant. This was all done confidentially. My friend did not want any repercussions as the young woman was a bit stroppy
I would suggest checking out the lease and adhering to what it says. If Mr Hitler complains, point out the terms of the lease. He wouldn't have a leg to stand on.
If he carried on, I would make a complaint to the management company.