The Golden Rule ? Sense or Bullshit?

[pocaracas]

For example "lie and manipulate people into doing what you want" is certainly beneficial. "Take whatever you can, as long as it doesn't bite you in the ass" is another. And yet, we do not consider these things moral.

Yes, that may seem beneficial for the individual, but imagine a tribe where everyone lives by that manipulating of others.
How long until the tribe breaks apart and its elements become scattered, outcasts and, ultimately, fail to survive.... because we need each other to survive. We are a social species and don't have many natural protections nor weapons.