There is no reason to think of another religion any different than your own.
The phrase might as well be, Do not do to other religions what you would not have them do to yours.
None of this is about showing how all religions are the same, or demanding everyone know about other religions. It is much simpler than that. While there are differences, and vast ones, and while there are at times striking similarities, none of them matter. We don’t reject the idea of ethnic cleansing only after being told which population is due to be annihilated—we reject it out of hand, not because of how different or similar the victims are to ourselves.
Just the same, regardless of their differences or similarities, we do not pretend that there are no other houses on our street; we do not pretend that there are no other people living in those houses, or that other families do not exist, other people. Regardless of differences or similarities to our own house or family, they are just other houses, just other people, just other lives. To pretend the other houses or people are inferior, for no other reason than that they are not our house and not our family, would elicit laughter from most people, since it’s so easy to point to houses that give shelter, or families that love and support.
Yet, for many people, such an attitude is what defines religion, even though it is just as easy to point to other religions, and their adherents, and see meaning at work. They are different or similar on many specific points, and so what. They are simply ways. And they are ways that can help us be decent to each other, rather than divisive. They are simply other religions.