I don't think we can *all* be imagining this... I think it's just a lousy station, just like the UA denizens complain about IAD employees.
Changing the culture requires the Station Manager to get involved. A caring station manager confronted with our combined ancedotal evidence would take the time to really drill it into people that AA's LHR culture is not in tune with the rest of the corporation, and it had better well *get* in tune.