The Browns moved into Senators territory. Griffith was paid a couple hundred thousand to let it happen. The ironic thing in this whole argument is "territories" only applied to teams in the same league (hence the Angels going into LA, the Mets into NYC etc.).
Angelos' claim to DC, even his exclusive claim to the TV market has always been bogus (see Braves/TBS broadcasting into every market, including this one, up until 2007. The Braves only stopped when TBS got the postseason deal w/MLB).
Now in fairness to O's fans, it looks like the poster in question caught a lot of flack on the O's board for his absurd post.....my experience has been most O's fans are okay re:the Nats, but the trash talkers tend to be the most vocal (and most ridiculous). I love that the Nats get under the skin of the haters in Birdland.