I've lived in Virginia and Maryland for more than 40 years. I know a lot
of people in both states. I've not encountered any Virginians who
"hated" Maryland or Marylanders who hated Virginia.
They must all be from Connecticut ;-)
I will admit the Wilson Bridge did create more interaction and newer
generations forget. In the 50s, Virginia was "over there, where those
people lived". You could climb a tree and see the Masonic Temple in SE
DC or near in PG. When you got down in Southern Maryland a little
farther it was far more pronounced with watermen arguing over who 'se
fish they were.
There aren't enough serious watermen these days to field a lacrosse league.