[What you're asking doesn't bother him. But the judgment in it, the contemptuous, implicit "you shouldn't be that way" that you aren't saying, does. So, with his intuitive sense for weak points, he turns your question around.]

You'd know about trying to be someone you aren't. Does that make you happy, Ritsuka? Has it ever? When you hurt things just by existing -

[He doesn't think he has to finish that sentence. Not with you. Spying on you for Seimei has given him all too clear a view of how you interact with your mother; how you let her define you.]