I think we all recognize the gravity of this situation, and it plays into our own fears of death. Some of us deal with it by wishing the best, and others deal with it by showing rude humor. Celebrity deaths and overall tragedies are obviously a go to for such behavior because it seems like we grew up with these people in image only. It seems like they aren't real people. Obviously none of us would make a ill advised joke in a public setting unless we were comfortable with the people we were talking to, but the internet is a different animal. We can make those comments with no problem and no consequence.
To quote noted scientist and compassionate humanitarian Dr. Jon Osterman: "I say this without condemning or condoning it."
Also: I don't think Macca's comment was really at the expense of Richardson's hardship, but rather towards all the media attention that it's bringing. Her family needs to be left alone in this ordeal. It's not going to happen, but I bet some privacy would be appreciated.