The problem with religion, because it's been sheltered from criticism, is that it allows people to believe en masse what only idiots or lunatics could believe in isolation.

Religious belief is without reason and without dignity, and its record is near-universally dreadful.

The weak spot of religion is its ridiculousness

Religion has ever filled the mind of man with darkness, and kept him in ignorance of his real duties and true interests. It is only by dispelling the clouds and phantoms of Religion, that we shall discover Truth, Reason, and Morality. Religion diverts us from the causes of evils, and from the remedies which nature prescribes; far from curing, it only aggravates, multiplies, and perpetuates them.

Religion is heavily laden with the kind of confirmation bias that makes people see their own faiths as true and all others as false. In other words, religion is replete with features to help people fool themselves.

[Religion] is innately irrational.

One of the things that is wrong with religion is that it teaches us to be satisfied with answers which are not really answers at all.

One of the problems with religion is that it creates in-group loyalty and out-group hostility, even when members of one’s own group are behaving like psychopaths.

ONE OF THE most pernicious effects of religion is that it tends to divorce morality from the reality of human and animal suffering.

Religion grants its adherents malign, intoxicating and morally corrosive sensations. Destroying intellectual freedom is always evil, but only religion makes doing evil feel quite so good.

Religion is the outcome of unresolved contradictions in the material world. If you make the assumption that it's man-made then very few things are mysterious to you: It would be obvious to you why there are so many religions; You will understand why it is that religion has been such a disappointment to our species - that despite innumerable revivals, innumerable attempts again to preach the truth, innumerable attempts to convert the heathen, innumerable attempts to send missionaries all around the world - that the same problems remain with us. That nothing is resolved by this. If all religions died out, or were admitted to be false, all of our problems would be exactly what they are now: How do we live with one another? Where, indeed, do morals and ethics come from? What are our duties to one another? How shall we build the just city? How shall we practice love? All these questions would remain exactly the same. Emancipate yourself from the idea of a celestial dictatorship and you've taken the first step to becoming free.

And then there’s religion, the source of the deepest fissure in the science-society relationship.

Religion carries two sorts of people in two entirely opposite directions: the mild and gentle people it carries towards mercy and justice; the persecuting people it carries into fiendish sadistic cruelty. Mind you, though this may seem to justify the eighteenth-century Age of Reason in its contention that religion is nothing but an organized, gigantic fraud and a curse to the human race, nothing could be farther from the truth. It possesses these two aspects, the evil one of the two appealing to people capable of naïve hatred; but what is actually happening is that when you get natures stirred to their depths over questions which they feel to be overwhelmingly vital, you get the bad stirred up in them as well as the good; the mud as well as the water. It doesn't seem to matter much which sect you have, for both types occur in all sects....

The human psyche has two great sicknesses: the urge to carry vendetta across generations, and the tendency to fasten group labels on people rather than see them as individuals. Abrahamic religion mixes explosively with (and gives strong sanction to) both. Only the willfully blind could fail to implicate the divisive force of religion in most, if not all, of the violent enmities in the world today. Without a doubt it is the prime aggravator of the Middle East. Those of us who have for years politely concealed our contempt for the dangerous collective delusion of religion need to stand up and speak out. Things are different now. ‘All is changed, changed utterly.