I watched that game, and Beckham was taunting the fans. Nothing to do with Trump. They filmed him on the sideline and he continued to taunt the fans for another 5 minutes, finally (even the commentator said it) the coach went over and talked to him.
Knowing Eagle fans, I can just image their response to that.
P*ss*ing on the fans, nothing that the NFL hasn't been doing to the fans on season.