The Golden Rule? What's That?

Here's a random rant...
Whatever happened to the golden rule? "Do unto others as you would have them do unto you." this was instilled in my head at a very young age and it made so much sense to me! You're nice to them, they'll be nice to you back. If they are not nice, be nice and eventually they'll be nice back.
It works with kids, mostly. But when you get older and meet mean, nasty people you can try drowning them in niceness, but they'll still be mean. My behavior and attitude can have negative and positive effects on others, but nothing I do will make a person change who they are and cause them to treat people differently.
So when someone does something bad to me like spreading a rumor or lying about me, the expectation is that I forgive them and I resolve the issue since I was the one hurt. I can understand this and don't necessarily disagree. What I do disagree with is that if you are being a jerk and hurting people then accept your responsibilities, apologize and accept the consequences.
Yes, there will be consequences. Words you say and actions you do cannot be undone. Eventually things can get better and it won't hurt as bad, but it's always there. Forgiveness doesn't mean you let people continually hurt you because they apologized. Change has to happen.
So what would happen if adults thought before they spoke and acted and responded the way they would want to be treated. I wonder how things would change. Something to think about.