http://wikitorweeyiuv6oyiuw3rnc57riyjmemsjc4pn7lgzvr4ewraah52id.onion/index.php?title=Tor&action=edit
So yes, criminals could in theory use Tor, but they already have better options, and it seems unlikely that taking Tor away from the world will stop them from doing their bad things. At the same time, Tor and other privacy measures can fight identity theft, physical crimes like stalking, and so on.