Such a rule is useless for moral guidance. But intelligent people think the CI is useful for moral guidance.
“Intelligent people” also think you shouldn’t switch in the common version of the Monty Hall problem. The whole point of this argument is to point out that the CI doesn’t make sense as given and therefore, that “intelligent people” are wrong about it.
That should have told you that your guess about what “universal” means, in this context, is wrong.
No, it tells me that people who think the CI is useful have not thought through the implications. It’s easy to say that rules like the ones given above can’t be made “universal”, but the same people who wouldn’t think such rules can be made universal are willing to make other rules of similar form universal (why is a rule that says that only Jiro can rob not “universal”, but one which says that only non-minors can drink alcohol is?)
“Intelligent people” also think you shouldn’t switch in the common version of the Monty Hall problem. The whole point of this argument is to point out that the CI doesn’t make sense as given and therefore, that “intelligent people” are wrong about it.
No, it tells me that people who think the CI is useful have not thought through the implications. It’s easy to say that rules like the ones given above can’t be made “universal”, but the same people who wouldn’t think such rules can be made universal are willing to make other rules of similar form universal (why is a rule that says that only Jiro can rob not “universal”, but one which says that only non-minors can drink alcohol is?)
None of the comments have not anywhere near the .CI as given. Kant did not define the .CI as an accessible function.
I have already answered your second point.