That feels like a punch to the gut. That his him stepping back just slightly from the shock, trying to melt into the shadow a little more; back into the darkness where he belongs.

He almost swallows the cigarette, because the smoke isn't getting into his lungs fast enough. He manages, somehow, to keep his voice from trembling somehow when he speaks.

"Why?" Good. Somehow he manages to keep that steady and not at all hurting. Any roughness on the edges is obviously from the cigarette smoke, "'f I didn't care about-- your furry little problem, why would I-- care about this? 've never said anything-- before, when you've mentioned it."

Or maybe.

"Or 's it-- 'cause it's Reg? Merlin, Moony, why would I care about that?" He can name a few reasons, but he isn't going to. This is about making Remus feel like this is okay. Like Sirius is okay, "You're-- wonderful. And he needs more wonderful in his life. This is-- this is only a good thing."

There. That's a good lie. That one he'd managed to make sound almost completely honest.