Sirius doesn't need to look at Remus to know he's--yet again--put his foot into it. He knows he has to make this right because there are so few of the Outsiders left, and they can't be fighting amongst themselves over the 'what ifs' and milk already spilt. Besides, he's always liked Kingsley--the man knows how to have a good time--and Sirius does regret upsetting him.
"Oh, bloody hell, Kings," Sirius groans. "Don't be like that. You know we'll help. You know we'll do what we can because saving one is at least saving one. But you know me. I can't help saying what I'm feeling. It seems like things are getting worse up there, and the kids are dying." He glances over at Vera and wishes he was close enough to touch her, because he can only imagine what she's thinking. "My brother's up there hanging on by a thread, trying to help, worried that he's going to die, too. And here I am, unable to do anything at all." He spread his hands apart in a gesture of helplessness. "You know I don't do well when I'm stuck in one place, with nothing to do."
He hopes he doesn't have to remind Kingsley of times in the past when Sirius has lashed out in situations just like this, out of hopelessness, fear, anger, and regret.