Showing him the mirror only make him to be sure he is Chinese.You'd better advice him to study the most scientific DNA which as evidence indubitable as one of your posts implied.
Race is the very foundamental thing and I wonder if it is necessary to show you hatred toward your own people I mean Chinese which within your own race.Why?
China if they know what we really look like.Tibetan just have plateau-red faces.
And as I know Indian tourists just simply regard the locals of Arunachal as Chinese.
It's our internal affair even if we forcefully entered somebody's house for we are the same people and you alien Indian just could consider Tibet as a good place one must take over.