After Yao Ying had been taken in by him, Li Guang quickly did what Yao Ying's father had ordered him to do --- even though he was feeling pity towards the weak little boy. Yao Ying's father had told him before that that he was doing all of this for Yao Ying's own good, so there was no reason for Li Guang to object it. After all, he knew his master really well... He wouldn't do something useless or something that could hurt his own son.
Not only that, but he could see the love from his master's wandering gaze towards Yao Ying --- even though he was pretty strict to the latter and masked his feelings really well.