Why should he be ‘allowed’ to decide how, when, and where he testifies? If it’s not under oath, it’s worthless.
All testimony to Congress is under oath in that lying to Congress is a felony.
You can't swear him in as a civilian, he could take the 5th all day long. Can't swear him in under the UCMJ, this isn't a court-martial. Yet.
The Committee is trapping the honey trap. Without Broadwell present, she can't get her story straight with his.