If you say so. Clint Murchison, first owner of the Dallas Cowboys, used to own the rights to Hail to the Redskins. When he tried to get a NFL franchise for Dallas, in 1959, the league was all for it. All except George Preston Marshall, owner of the Redskins, and back then granting of new new NFL franchises had to be unanimously approved by the team owners.
At the time there were neither NFL teams in the South, nor an NFL TV contract. Marshall kept all the Redskin players white, and had his own TV contracts with TV stations in the South, so his team was very profitable, while losing consistently. Not unlike the Cowboys of today...
The Cowboys were going to field black players, which would give them a competitive advantage over the Redskins. Marshall thought, correctly, that most football fans in the South would rather support an integrated team that won, than a lily white team that lost, so he refused to approve a franchise for Dallas.
The Cowboys ownership, looking for leverage, found out that Marshall did not own the rights to Hail to the Redskins, and purchased it. They sent Marshall a notice that if the song was used in anyway at Redskins games, he would be sued.
Some of the other other NFL owners raised the idea that they could all withdraw from the NFL, and form a new league, with new franchises in Texas, and Minnesota, leaving the Redskins as the NFL's sole team, to scrimmage themselves. While that would have guaranteed the Redskins a .500 season, Marshall knew he couldn't sell tickets, or TV rights, to that, and he gave in. Dallas got an NFL franchise, and the Redskins got the rights to their fight song.
I liked the “Miami Dolphins Number One!” song, and then the Oilers stole it.
I’m guessing they didn’t want to lose the Dallas market (and beyond) to the AFL Dallas Texans.