What worries me about religion is that it teaches people to be satisfied with not understanding the world they live in. - Richard Dawkins

I am against religion because it teaches us to be satisfied with not understanding the world.

The total amount of suffering per year in the natural world is beyond all decent contemplation. During the minute that it takes me to compose this sentence, thousands of animals are being eaten alive, many others are running for their lives, whimpering with fear, others are slowly being devoured from within by rasping parasites, thousands of all kinds are dying of starvation, thirst, and disease. It must be so. If there ever is a time of plenty, this very fact will automatically lead to an increase in the population until the natural state of starvation and misery is restored. In a universe of electrons and selfish genes, blind physical forces and genetic replication, some people are going to get hurt, other people are going to get lucky, and you won't find any rhyme or reason in it, nor any justice. The universe that we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, no good, nothing but pitiless indifference.

Admittedly, people of a theological bent are often chronically incapable of distinguishing what is true from what they'd like to be true. (p. 135 of the Black Swan paperback edition of 2007)

Such delusions of grandeur to think that a God with a hundred billion galaxies on his mind would give a tuppenny damn who you sleep with, or indeed whether you believe in him.