not so sure of it being opposite equals, rather a need of balancing the initiated action,
little proof other than short range consequences for now

There is a law in physics that says that for every action, there is an equal and opposite reaction. However, we have free will, so our reaction will be equal, but we choose the direction. We can turn it back on them which causes war, or we can internalize it and become sick, or we can deflect it to a positive reaction. Like if someone call you a fool, you can either call them a fool back and keep it going, maybe getting worse, or you can believe them that you are a fool, internalize and let it take you down, or you can smile and say, Thank you! That is your external response, you may still internalize, so learning a stress relief technique like EFT would be good.

I am a sixth degree black belt in Karate and I can tell you the law of action/reaction works because that has been perfected in karate to give tremendous force and power to blocks, techniques, punches and to a lesser extent, kicks. Just for one punch alone takes four hip movements this creates a momentum like cracking a whip and explodes in the punch being thrown. This of course must be coupled with the torque of the arm and wrist counter the motion of the shoulders all in perfect sequence. In other words all of this motion is converted into energy of the actual punch, so all of this pre-power generation is the initial action, the reaction is the power it generates behind the punch.

There is also a law of diminishing return, so if I take two balls and hang them in a row. I then pull back the first ball and release it, it crashes into the second ball the second ball moves out and the first stops dead. The second moves out not exactly the same distance but just a little less before returning to hit the first ball again. At this point the second ball stops and the first ball flies out at an angle again, not as much as the second ball. So in this way eventually both will come to rest.

The interesting thing is on the spirit level these rules seem opposed, so something I send out returns back more than I had sent out.