Because religion (and politics) are both about institutes concerned with social organisation and control.
They both make use of our deep desire to search and find the truth about ourselves and the universe.
Through a process of conditioning we are given all kinds of ideas and concepts about this or that being "the truth". And the reason we accept these finds it source in our need for security. because we our not aware of the truth which lies behind our existance.
Once we have accepted all these concepts and ideas about ourselves and the reality we live in, we identify ourselves with them.
Once we identified ourselves with them, we feel the need to protect them, because we think we have to defend ourselves.
Every insult, doubt or questioning about everything we have ourselves identified with, is wrongly seen and interpreted as an attack from the "outside".
This is a reaction out of fear and out of ignorance about our real nature, being ourselves expressions of the Devine truth.
Religiosity is a personal issue, which arises from our awe and astonisment of our own existance, which we witness through our conscious.
Therefore, religiosity, is something which has to and can only be lived as a lively experience and expression of life itself.
And life in all its potential, can hardly be enchained or bound in a set of social rules to live by.
Live according to that which feels to you as being good. Simply look into your heart to feel it. Free yourself of all what they told you, whatever it was, or might be, so that you finally can start living life the way it was meant.