I agree with whitewave, any faith is a gateway into another and potentially more destructive belief system. The reason is that faith is, in essence, believing something without any evidence or rational proof. It discourages logic, questioning, proper informed debate and rational scepticism.
There is an interesting difference in levels of faith between my sister and I who had the same religious upbringing. We were both baptised catholics and were both sent, originally, to catholic schools though and, though our parents did not attend church, I was sent to church on Sunday mornings and also attended catechism. I had a first communion though wasn't confirmed while my sister was youunger and kept at home.
We have turned out very differently. Terrified of the idea of hell and sin I was quite religious up until the age of about twelve when my mother stopped sending me to church. I started to question the idea of a 'merciful God' burning souls in hell for ever and, once that keystone disappeared under rational consideration the rest of the edifice of faith fell. I am now an atheist and very sceptical of faith though I am still a cultural Christian and value the whole moral system of faiths unless they make people suffer or become extremists.
My sister, who escaped some of the 'brainwashing' has, however, embraced faith in genereal and jumps headlong into belief systems whether they are irrational or contradictory. She is a low church Christian and church-goer, a socialist and a vegetarian. She has so restricted her ability to think independently that she cannot deal logically or rationally with any social, political or personal topic. She cannot debate any issue without becoming heated and angry and she went through a phase of saying, 'You cannot think that!' without perceiving the restrictive, self deluding quality of her words.
Through my sister's blind faith and very prejudiced views of those who disagree with her I can see how young people can be drawn into dangerous mindsets where they are a threat to others. My sister was a nice girl and very tolerant once and her 'moderate' beliefs have hardened into a sort of fanaticism - which she would not recognise or acknowledge.
I think faith is a slippery slope which starts mildly and grows. It is a danger to society when adherents are lonely, socially outcast, addicted to anti social substances, failres at work or play, or who feel marginalised or alienated in any way. A faith can provide a vehicle for vengeance against the rest of the (happy and contented) world.