Reason for Qianlong tone

The point of view of Qianlong in his letter to England is very arrogant and condescending. The reason for this is because Qianlong has no idea what his actions will bring. He's been raised thinking that he's the best and has the best empire in the world. He believe that he needs to help or trade and that everyone else is beneath him. It's just plain old ignorance to the reality of his country and people that makes him write this letter in that tone.