"You really don't care about people at all, do you?"
A great many people see Sherlock now, the internet sensation, yet fail to observe.
It's so simple it's elementary. It is one of those instances where the reasoner could produce an effect which would seem remarkable to his neighbor, because the latter has missed the one little point which is the basis of the deduction. Could, but doesn't.
So Sherlock explains, not because he is vain (he is) or likes the sound of his own voice (he doesn't care) or because he wants John to understand it (he does, but only if John figures it out himself). He explains it to Molly because he doesn't have his scull and John and Mrs. Hudson still have to think he's dead and he never enjoyed heart-to-hearts with Mycroft.
"I imagine you all think so, but I know people."
He knows the meaning of the slightest movement of the eyebrow, he knows why people brush their hair this or that way, why they stand how they stand or breath how they breath, or do what they do and how they do it. He knows people as well (better) as chemistry.
He wouldn't know them if he didn't spend a lifetime studying them. And he wouldn't study them if he weren't interested. And the only reason he could be interested in people is if he cared. If he wanted puzzles without people, he would play chess and study quantum mechanics and devise a theory of everything.
So it baffles Sherlock that nobody understands this preposterously elementary chain of reasoning.
AN - just a drabble/rant at fangirlfriend.