I have no problem with players expressing disappointment. What I DO have a problem with is them not congratulating Stewie for winning. That's just low class and poor sportsmanship. From the time little girls can bounce a ball, win or lose, the coaches and team line up for the hand-shake line.
We constantly criticize coaches or teammates who don't give kudos to the other team when they lose. Even if your team played terribly, players/coaches almost always give credit to the other team. When they don't, they are called out. Why is this any different?
I certainly don't expect Wilson or Thomas to be thrilled Stewie won the award. I haven't seen all the Thomas quotes so I'm not sure if she congratulated Breanna, but I've seen zero quotes from Wilson congratulating her. That's the issue, and both of them should be criticized for it. Zero tolerance for poor losers.