Qianlong is quite spiteful here. From a distance one might think he is acting enchanted of A'rou. It might even seem hurtful to Ruyi. But he's actually setting everyone against A'rou on purpose. He has no light in his eyes when he talks to her. He is 'doting' on her intentionally in this moment to piss everyone else off and get them to bully her. Such an underhanded man. Even though in this instance we might not be so angry, his underhanded nature really is ugly...