It seems to me the refusal to answer the question "when will everyone be paid back in full" is directly related to "I'm still paying you guys interest"
he is adding debt on top of debt he cannot pay any time soon, if ever.
His only alternative is to disclaim debt that he might be able to pay back. However, I definitely agree that more communication would be better. It's entirely possible he's actually trying to assume a larger share of the burden for the bad loans than is fair. But if he wants to convince people of that, he needs to make a clear and complete case. (Because it's also very easy to say "80% of my loans went bad, and I'll split that cost with my investors" when only 15% of the loans went bad to basically steal from your investors.) Transparency helps credibility, but if you're lying, you take the risk you'll get caught in the lie.
However, if he's going to ask his investors take the all or most of the burden for a bad loan, I believe they have the right to know who defaulted. And if those who defaulted want to claim that he's lying, they should be given that opportunity so the investors can assess whether they're actually being treated fairly.