He frowns at him for a long moment, then looks away. "Fine. Do your thing, Mohinder."

If this starts looking bad, though -- or if it starts looking like Arthur has Mohinder working on a way to mute his abilities -- he'll put an end to it. He knows where the lab is; he knows where Flint is. If worse comes to worst, he'll murder the latter to destroy the former or just force Flint into doing it for him. It'll depend on his mood, if and when it comes to that.