I agree that it’s possible to arrive at the conclusion “pain is bad” as an individual, but I guess what I’m arguing is that there’s no absolute hard line on what is and isn’t ethical. Each individual person might have their own personal line, but there is no guarantee that line will be the same as another person’s. Case-in-point, a psychopath is someone with reduced or no empathy for others. They may very well not consider pain in others bad at all.