Not sure I buy that. No one is forced to be an executioner. You sign-up for the job. Only someone who is "OK" with that would do it. As for the public, back in the day it used to be a community event to go watch the hangings. Again, if they didn't like it they would have stayed home.

Sure, but it ends up messing them up. Being an executioner is rough work, psychologically. And it's not just the executioner - it's the other staff, the witnesses, kind of everyone involved with the process. Making it more of a sanitized medical procedure, rather than a violent act with blood flying everywhere, reduces that load. And again, the public perception of the process matters, too. We're long long past the days when the public would take the kids out to see a hanging as a public spectacle. Times have changed.

Not saying lethal injection is better - obviously it has its own issues. Just that the reasons we don't use the guillotine are probably more about everyone else in the process, including the public, and not the prisoner (who would probably have the least painful death using that method than any other).