As someone who watched the exchange, you're completely wrong in your characterization and in fact Benanke agreed with Warren on almost anything.
He questioned the figure that is was based on only one study and would need to see others try to quantify it.
Where he questioned Warren and what you and Warren didn't understand (and I like Warren and love that she is tough on banks) is that Bernanke was trying to explain that the market is misunderstanding risk and that's why they're getting this supposed bailout but that it most likely misplaced and that they very well could not be TBTF and stand to lose a lot.
Go and actually watch the exchange. If you actually think Bernanke is lying or for TBTF or arguing with Warren, then you're dead wrong. He agreed with Warren that they need to get rid of TBTF and is trying to do so with the tools he has. He agreed with 95% of what she said and only disputed the idea of risk in the market which she would have no idea knowing about since she has no clue how to measure it at all.