This situation was dancing into territory where Nathan had to find a distraction to sit back and not go right to Peter as the truth was unveiled to Angela, to shield, protect and fix before anything had a chance to go horribly wrong. He wanted to, and he would if he felt it was necessary, but right now he wanted to give Peter a chance to say what he wanted to say to her. Another response from Claire was a well-timed reason to stay put momentarily, so he responded, eyes still on the scene playing out before him.
His derisive snort at Angela's words was mental only and he had to focus again on the computer screen to stem the silent tirade that threatened to follow. He'd faced this with Peter, the knowledge of what he hadn't done there in Peter's timeline, but from where he sat, his mother didn't have that same luxury of looking where both ends of her choice had led her, recognizing the capability of great wrong and great right. Each time she'd made the same damned choice. What more, she'd gone on to keep putting the Company and power before her children. He didn't look at it as being better than his mother, as he had plenty of marks on his record that made him in some ways despicable – it was just the reason he didn't trust a word she said.
What mother would rather believe her child's destiny - and not even just her child, but her favorite - was to die with such an unshakable certainty as Angela Petrelli had demonstrated? He'd never been able to wrap his mind around that, and it had only been worse when he had finally realized it was still time to listen to his own doubts, his own conscience and the voices of people who were far better, far more good than he could hope to be, rather than the supposed certainty. It had been the right thing to do, doing that, but she'd still thought he was wrong even after the city had been saved. Yet now, now she saw the light?