Don’t just believe what others say
The problems with Hitler’s and Stalin’s teachings were that they were too much like religions. They both contain things you have to believe even if reality says something else.
It is important to think for yourself. This is not only true for religions, but for politics and everything else.
Don’t believe anything that you don’t have a good reason to believe!
There doesn’t exist a society on earth where people have fared ill because the people in power have been too wise or too reasonable.