Note: This is not meant simply as an insult. Yes it is insulting to certain religious people, but I think it is warranted. I can support all points with quotes and references to literature, and references to real events in society.
I don't really think it matters a whole lot whether there is a god or not, what makes a much bigger difference are the symptoms of religion.
Modern religion says:
Turn the other cheek, be modest, obey your leaders (except when it contradicts your religion), devote your resources towards helping the weakest instead of the strongest.
This encourages the following attitudes:
Society embodies a cyclical process with certain pillars which are not supposed to change (the overall structure of society), technology is mainly important in how it helps the weakest or in how it promotes traditional forms of social organization, strength power or assertiveness are not virtues, there is an (imaginary or actual) "alternative world" or "background world" which is somehow ideal, there are "ultimate causes" for people and the universe.
This leads to the following behaviors:
Suicide (due to depression, for terrorism, etc. - there is an "alternate world" to compare this world against unfavorably), conformity (society is cyclical, on some level it's basis is unchanging), stupidity (lack of scientific achievement, why bother anyway? reality is the "spiritual"), harshness towards some subset of criminals (they have "free will", others are simply "ill" - we could include this in 'stupidity')
This sickens society:
Modern religion is parasitic, preying on a person's weakness, sometimes in a benign manner, often not. Religion limits society more than necessary. Religion makes people more willing to die. Religion generally squelches and saps the real human 'spirit' (our drives which make us stronger and better).
Modern religion is like genocide with impunity, only worse.
Thoughts? (I mean it - I will openly discuss and I will change my mind where I am shown to be wrong. Thank you respectfully.)