The Tianyan Token was lost from his hands, and it was swindled away, which is certainly not a glorious feat.

If he admits it, as the head of the Duanmu Family, he will become a laughingstock.

If he doesn't admit it, it would confirm the Royal Dynasty's ulterior motives.

Su Shi'er did this clearly to humiliate and retaliate against him for pressuring the Illusory Star Sect earlier.