When things are done that bring pain and suffering to a people, everyone shares that pain and suffering. Whatever is done to one ripples through the thought stream in the form of fear, depression, and heaviness. That is the karma I believe in, and it's observable not a fantasy theory.
Belief has always been a barrier to insight.
Q:What about people who don’t believe in karma?
A:Karma is a fundamental mechanism of our existence. It applies to everyone, regardless of belief. Anyone can understand the reasonableness of karma, and all great spiritual authorities have taught the principle of karma: that there are reactions to our actions. In the Bible, for example, we find the statement of Jesus Christ: “As you sow, so shall you reap.”http://www.krishna.com/law-karma