It's probably for the best that Sam clarifies that he's talking about his own world; Crowley knows that the rules are different, but he tends to forget on occasion and the ridiculousness of everything that's being said would not have helped with that.

"That's the most stupid thing I've ever fucking heard." Not at Sam himself, just the rest of it. "Turning humans into demons would've tipped the scales much too far in Hell's direction, unless humans can become angels as well?"

That sounds even worse, honestly, and he can't imagine any human wouldn't lose their mind at the monotony and loneliness of Heaven.