I can only assume that those who wring their hands in anguish at black humour and bad taste are lucky enough never to have been involved in the sort of unpleasant situations the jokes celebrate.
The times when I've been involved nasty situations involving lots of bits of dead people, mutilated children, slaughtered innocents and the like have been the times when the jokes have come thick and fast. They're a safety valve - without black humour we'd all go mad with the sheer unremitting horror and unfairness of existence. It helps us keep buggering on in the face of enormity.
A po-faced attitude is quite common, though. I was in hospital a month or so back having suffered a heart attack. It was a worrying time for the family, and as they all clustered round the bed where I was covered in wires and gadgets I tried to defuse things with some off-colour remarks. My son's girlfriend was absolutely disgusted, I discovered later. Apparently she wanted to hit me for making jokes about sick people and nurses, a though I had somehow demeaned the holy nature of the hospital. It was quite cathartic telling her to fuck off when I was discharged.