Somehow, in the midst of her story, he's forgotten his own misery and impending guilt. Right now, all that matters is her. And so he actually laughs - not at her, but sympathetically, warmly. He kisses the crown of her head tenderly, and strokes her hair, saying -

"Don't be sorry. Sonia, I only said no because I'm sparing you more of the same. I'm not an honest fuck. I am, by very definition, a dishonest fuck."

He wraps his arms around her and snuggles her in tightly against him, letting her cry herself out. After a moment, when it seems like her sobs are dying down a bit, he asks, "There's really never been anyone? Not even on Beta?"