Keith was timid from the moment Damon showed up in the training center, and things went downhill when Damon announced that there will be a competition to determine Talia's trainer.
Keith was confident in his skills, but in this case, he was going against his Alpha. No one wins when he goes against Alpha. That's why Damon is Alpha; he is the best. In everything.
However, seeing that Damon was unusually non-intimidating and he was not even trying to train Talia, Keith found a bit of courage in the back of his heart as his competitive spirit urged him to speak up.
Keith showed Talia an effective kick and she practiced, while Damon only held her from behind. The victor was obvious. Right? RIGHT!?
Wouldn't it be glorious to have a victory against an Alpha as a badge of honor? And Damon has a fierce reputation as an Alpha who never lost a fight.