How dangerous is the one who doesn't believe in SIN?

 Dangerous as can get. 

Sin means that your action in this life has a judgement/consequence (by the creator) in the next life.

The Hereafter..

Un-belief in SIN means you can do what you want.

Are most people satanists?

 

There is a thin line between satanism and most peoples beliefs since they both have much in common:

- Promote sexual promiscuity

- Worship of desires

- Are Atheists

- Individualists

-Understanding of will, that they are Gods in themselves, they will and so happens

-Mockery of God or denial within the culture

-Unbelief in the Devils influence, the devil himself, thereby not recognising evil or recognising evil only in its shallow form  divulged from its details and  intricate details and not that which is connected to the unseen) 

-Paganism, either through the Atheist route or associating partners which God.

-Use of intoxicants

Purifying worship

 Islam simply brings purity in worship to correct man worship of the creator. It is not a war for politics or power simply news of how to pray and fulfil man's need for worship and thanks to the creator. 

The arguments of philosophy and whims and desires are left voided because islam is not interested. It is interested in what has just been mentioned.