How much of this is a question of what filth level people accept as normal?
Maybe Bal'moreans just want cleaner than people elsewhere and complain more.
I had a similar thought. For instance, New Orleans may well be dirtier, but folks there are so laid back they don't complain (and the government there is so inefficient that complaining would be pointless -- my son who lives there, echoing a 19th century comment about NOLA, says "If you think of it as an American city, it's terribly run. If you think of it as a Caribbean city, it's really remarkably well run.")
Of course, Baltimore is also peculiar in that urban blight is not concentrated in neighborhoods: there are blighted blocks next to reasonably nice blocks. If you go up in a high building you can see it, random concentrations of derelict or run down buildings across the street from or even surrounded by blocks of well-kept ones, so that might contribute to extra complaints, even if the overall level of filth is no greater than in cities with bad neigbhorhoods rather than bad blocks.