I’m not convinced that “offense” is a variety of “pain” in the first place. They feel to me like two different things.
When I imagine a scenario that hurts me without offending me (e.g. accidentally touching a hot stovetop), I anticipate feelings like pain response and distraction in the short term, fear in the medium term, and aversion in the long term.
When I imagine a scenario that offends me without hurting me (e.g. overhearing a slur against a group of which I’m not a member) I anticipate feelings like anger and urge-to-punish in the short term, wariness and distrust in the medium term, and invoking heavy status penalties or even fully disassociating myself from the offensive party in the long term.
Of course, an action can be both offensive and painful, like the anti-Semitic slurs you mention. But an offensive action need not be painful. My intuition suggests that this is a principled reason (as opposed to a practical one) for the general norm of pluralistic societies that offensiveness alone is not enough to constrain free speech.
I’m not sure which category the British Fish thought experiment falls into; the description doesn’t completely clarify whether the Britons are feeling pained or offended or both.
Robin Hanson has identified a breakdown in the metaphor of rationality as martial art: skillful violence can be more or less entirely deferred to specialists, but rationality is one of the things that everyone should know how to do, even if specialists do it better. Even though paramedics are better trained and equipped than civilians at the scene of a heart attack, a CPR-trained bystander can do more to save the life of the victim due to the paramedics’ response time. Prediction markets are great for governments, corporations, or communities, but if an individual’s personal life has gotten bad enough to need the help of a professional rationalist, a little training in “cartography” could have nipped the problem in the bud.
To put it another way, thinking rationally is something I want to do, not have done for me. I would bet that Robin Hanson, and indeed most people, respect the opinions of others in proportion to the extent that they are rational. So the individual impulse toward learning to be less wrong is not only a path to winning, but a basic value of a rationalist community.