Rotten at the core.
From my study and observation, belief systems all have one thing in common, when you peel away the layers, investigate them in depth, they are all rotten at the core.
They are all based on fear, and are all designed by humans to control humans.
There are some belief systems that cover this rotten core very well, so the people that adhere to these systems rarely see whats underneath, and if they do get a glimpse of it, they are so caught in the circular logic that these systems create, they cannot accept that this rotten core even exists.
Many religions use the "you have no right to question beliefs, you must accept on faith that these beliefs are true, or you will be punished", this is an effective way of preventing believers from looking into the incongruencies in the belief system. This way people never get beyond the surface face of the belief system. On the surface many belief systems appear benign or harmless, but did a little deeper and you can see where the rot begins.
If someone outside the belief system questions its validity, they are labeled as enemies, trying to destroy the belief system. So for the people at the core of these systems, it is a win/win situation, and the people they are controlling stay trapped.
In some political belief systems, the punishment for questioning those at the top, is death or imprisonment. Many religious belief systems use the threat of damnation after death, or excommunication from the group, as punishment for questioning the belief system.
It was only when I honestly examined the belief systems I was caught up in, that I realised how I'd been fooled by all the clever tricks that are used to blind people to what is really at the core of these systems. By following a belief system, you give up your power to those in control, and those in control are not some made up supernatural being, they are as human as you are.
spud