To be completely honest, I made a similar joke once.
The writer David Foster Wallace killed himself. My professor was talking about him, and in passing mentioned that she'd criticized his last novel. And I said maybe the bad review pushed him over the edge.
Of course, that wasn't a personal friend of hers, so it's not exactly the same. But... some people just have a somewhat darker sense of humor. Hopefully he apologized, but it's not something that I feel is unforgivable.