Of course you don't have to be religious to use the Golden Rule. But it can add an extra dimension of understanding.
For example: this past week I've had to shuttle my Dad around for various hospital visits. We use his van because it's been easier for him to get in and out of. And he has a handicapped tag for the vehicle.
Some others who have used the van (with his permission) while he was laid up took advantage of that tag. They freely admitted they parked in handicapped spaces even when they weren't transporting Dad -- to them it was just a perk. Why not take advantage of the privilege when you have it?
I haven't been tempted because of a previous experience. I vividly remember a time when we were taking my grandfather out to a restaurant. He was very frail, and since very step was a struggle, the fewer he needed to take, the better. When we arrived, the both handicapped places were taken -- by cars with no handicapped plates or tags. The careless selfishness of those drivers created additional unnecessary hardship for my grandfather.
I hadn't really thought about that experience for years, until I got behind the wheel of Dad's van.Then I remembered. And so I've not been tempted to use the handicapped parking places when I'm not transporting Dad. Because I don't want to cause hardship to someone else.
“Teacher, which is the greatest commandment in the Law?”
Jesus replied: “‘Love the Lord your God with all your heart and with all your soul and with all your mind. This is the first and greatest commandment. And the second is like it: ‘Love your neighbor as yourself.’ All the Law and the Prophets hang on these two commandments.”
Matth. 22: 36-40
Sure, you can just live by the Golden Rule (that would be the second commandment Jesus talks about) and forget all that God stuff. But for me, the first is important, too. Because I believe that God gave me that earlier experience with my grandfather to help me understand what I need to do now. Others did unto us, so I know how not to do unto them.