If he started complaining and kept running away after hearing all that, people would take the opposite stance and say he is an asshole and that his reaction is unbelievable. And if Tomori's intervention really did fail, what in the world could reach such a broken Yuu? The story would end right there
That's the writer's fault for getting his character in such a huge mess, I can't have my character turn into a maniac over quite some plot duration to just have him turn back to normal in less than 3 minutes. Tbh, there was no need for a full recover from that alone, why not test her further if she stays true to her word?

And whether he is an asshole or not is not even clear to me if we consider how he used his power, remember how he "saved" the girl back in ep 1?