The laughter comes there; John snorts, leans over a little as he chuckles, because as if Sherlock would do something like that. It would be completely illogical, honestly. Wouldn't make any sense at all.

"Why would you make a hat out of someone's skin?" he asks while he's still laughing, and takes a deep breath as he pulls himself up straight again. "Why wouldn't I be? It's not like I think of this as torture."

He's already spent basically a full day with Sherlock, and it's looking like this one might just become that too. And he has no problem whatsoever with it.

People don't spend that much time with someone if they don't think it's a great idea, do they? And enjoy it, or at least... pretend to. But for him it isn't pretend, so of course. Of course it's a great accomplishment.