If you've said the position correctly, there seems to be a fatal flaw in that position. I realize, of course, that I've only thought for 5 minutes and that they're domain experts and been thinking about this for longer...but here is the flaw:
If we believe that an AI can convince Person X who has seen its algorithm that it is Friendly when it isn't actually friendly, then we shouldn't trust Person X to judge the algorithm's Friendliness anyway. Why would someone who makes the wrong decision with less information make the right decision with more information?
Edit: I guess knowledge of human biases could make the AGI in a box slightly scarier than uncompiled source code of said AGI
I think the key difference is that the AI can convince the person. You might say that a person is fully competent to judge the Friendliness of the AI based solely on the code, and yet not want a (superintelligent) AI to get a chance to convince him, as superintelligence trumps intelligence. The difference is whether you have a superintelligence working against you.
AI Box Experiment Update #3
Tuxedage (AI) vs Alexei (GK) - Gatekeeper Victory
Tuxedage (AI) vs Anonymous (GK) - Gatekeeper Victory
I have won a second game of AI box against a gatekeeper who wished to remain Anonymous.
This puts my AI Box Experiment record at 3 wins and 3 losses.