Jim knows that there's not really anything he can say that would help justify that kind of thing, and feelings aren't exactly subject to logic, no matter what Spock says. Having a good reason for lying doesn't take away the guilt.

But maybe there's a small olive branch he can offer. "There's no way we can tell everyone, but my senior crew... they can handle it." Jim draws in a breath, aware that what he's about to say will skirt the edge of classified information. "We found out something, about Starfleet. A secret branch of the service that's dedicated to developing advanced technology. They were going to use us to start a war with the Klingons, and it scares the shit out of me to imagine any Nexus technology in their hands."