Believe it or not, sometimes being over-the-top polite and accommodating to people gets them to take a counter-point seriously. You just have to wrap it in a lot of stuff about how they're obviously right and you're clearly completely wrong. Once in a while catering to someone's need to be right lets you slip an idea past it.

It comes off as 100% condescending and patronizing (which is what it is.)

Do you think there's a better way I could have handled that user, given what was attempted by myself and others to no result?