Six months ago an old friend of mine was murdered on his doorstep. This week his killer was sentenced to life imprisonment. In both cases, the first I heard of it was when someone I follow on Twitter posted a joke with a link to a news story. Both jokes were whimsical rather than callous — both were, in fact, musing on which Sunday evening television detective would most likely solve the crime — but whimsy in these circumstances feels like callousness.