What's the problem when the lamp shade is removed by mitch

The moment when Mitch tears the paper lantern off the lightbulb is a shocking violation, and it mirrors the rape in the succeeding scene. He has penetrated her illusion, forcing his way into the inner sanctuary of her game. It is a harsh act, and Blanche stumbles from it as if struck. Her magic has flown away, and she is left only with hated realism.