Amoureux et jaloux de la liberté humaine, et la considérant comme la condition absolue de tout ce que nous adorons et respectons dans l'humanité, je retourne la phrase de Voltaire, et je dis : Si Dieu existait réellement, il faudrait le faire disparaître.
Source: God and the State (1871; publ. 1882), Ch. II; Variants or variant translations of this statement have also been attributed to Bakunin:
The first revolt is against the supreme tyranny of theology, of the phantom of God. As long as we have a master in heaven, we will be slaves on earth.
A boss in Heaven is the best excuse for a boss on earth, therefore If God did exist, he would have to be abolished.