"I hear you, kid, you don't have to convince me. But they're something more to her. You're asking me why she might be upset and I'm giving you an answer, I don't think I can do any better than that."

And maybe that makes him heartless, agreeing that they're not human at all. He does feel a certain amount of sympathy. They're just children, and what happened to them is horrible. But Sinclair's feelings on the matter aren't going to save them. It's what he says and who he says it to that makes a difference. That's the only thing he can control here.