Silenced as in ordered to do thus and so by POTUS himself. Director of the CIA is a political appointment.
Disobey the illegal order that is a political coverup. Go to the steps of the capitol and lay out the whole, unvarnished, treasonous story.
Be sure to include that HE lied when he testified that the video caused this. Say who told him that was the official lie they were going with and who ordered him to advance it.
Bring proof that you as CIA director have.
Trust the nation to protect you, and to reward your honesty.
Lives,
Fortunes,
Sacred Honor.
If you are ordered to go before Congress and lie, then you have both a Constitutional and moral duty to resign rather than commit a crime like that.