Why interpret it as "do what they would want, not what you would want" ? Because at its root it's asking you to have empathy and compassion. You simply can't achieve both those things without putting yourself in their shoes, and then trying to feel and understand the way they do. At that point, when you are them, you act in a way they would want, and it becomes a compassionate act.
When I was saying before that this benefits you in the end, that's true, though there is no actual reciprocity expected in this rule. It really is all about just doing good for another person.
Ask a theologian about it some time. They explain it better.
I interpret the Golden Rule as it is written -- a bad rule, from an intolerant time where everyone was expected to be the same. It never really applied, but now we have the cognitive tools to identify it as bogus.
I just don't think "treat people with kindness" is what the Golden Rule says. That might be the intent of the people who reference it, but the Golden Rule literally says, "Treat others how you wish to be treated", which makes the assumption that "how you wish to be treated" is universal. I agree, realistically one should treat people how they wish to be treated, but that's not what the Golden Rule says.
My point re: calling girls dudes is that you simply cannot know if a girl does or doesn't want to be called a dude unless they express a preference, which may or may not happen. Some girls like to be called dudes (A), and we should do to others what they like us to do to them (B), therefore we should call those girls dudes (C). (B) is not the Golden Rule as such, because how I'd like to be treated doesn't apply to someone else (see nomad flint worshipers above).
I just want to be clear that what you're saying is not what I have issue with -- yes, we should definitely treat others in the manner in which they'd prefer to be treated. My issue is entirely with the characterization of this as the "Golden Rule". I don't believe that's what the text of the Golden Rule reads as.