Our level of thinking is not the same at all even though we are of the same being. Take the case of a dog who are taught to bark from birth, and so he barks the whole of his life. He will resist change and if provoked will bites. Just how are we being taught from birth, firstly we honour our mother and father no matter how wrong they are. Same like religion, what we are taught to believe from the day we are borm, would be glorify and defend till death. That explains the division between Islam, christianilty, buddish, Hindus etc.