What is the test for terminating a defendant's right to conduct his own defense?

Without directly denying that self-represented defendants have a right to stand mute, the majority asserts that in this case the trial court properly terminated defendant's right to conduct his own defense because he had engaged in " 'serious and obstructionist misconduct' " that " 'abuse[d] the dignity of the courtroom.' " (Maj. opn., ante, p. 591 of 10 Cal.Rptr.2d, p. 598 of 833 P.2d, quoting Faretta v. California, supra, 422 U.S. at p. 834, fn. 46, 95 S.Ct. 2525, 45 L.Ed.2d 562.) But in what respect is mere silence obstructive? And how does such silence abuse the court's dignity? These are questions that the majority does not, and cannot, answer.