You miss the context, though. The unnamed writer (presumably Prachett) advocated suicide as something positive and talked an audience member into suicide. All

You miss the context, though. The unnamed writer (presumably Prachett) advocated suicide as something positive and talked an audience member into suicide. All for the sake of feeling better (or, rather, not feeling). For Wright, humans are made in the image of God, and to kill yourself as if you were a horse with a broken leg is a travesty. To advocate doctors killing people, even if they want to be killed, is to treat people in an amoral, atheistic way that destroys civilization. And in the comments, Wright regrets that he did not have the gall to stand up and do something about this evil. It's a bit like, if you knew what would happen when Jar-Jar proposed giving Palpatine dictatorial power, regretting not actually doing something instead sitting while everyone else pulled civilization down around you.