Here’s the thing: I certainly get why “Everything happens for a reason” can be irritating to suffering people when it is meant (or taken to mean) “God is doing shit to you to make you suffer”, particularly when the suffering is innocent and not self-inflicted.
But the truth is, the Christian tradition does not teach “Everything happens for a reason” when it comes to sin. Sin is radically unnecessary. It is entirely negative and often completely irrational. It happens, in the end, for *no* reason because it is the act of a creature asserting its Nothingness.
The paradox is that a strict Materialist, not a Christian, is bound by his philosophy to assert that absolutely everything happens “for a reason” and that reason is and can only be that everything which ever happens is the latest outworking of the interplay of blind and inexorable time, space, matter and energy. Materialism is bound by its tenets to assert that everything that has ever happened or will happen will have happened “for a reason”: because of the blind physical causes that happened just prior to the Bad Thing.
Christian theology insists that, in the end, sinful things happen for *no* reason. They were not necessary, they were not willed by God, and they are entirely gratuitous acts of abused freedom that, paradoxically, result in enslavement to evil that God hates.
What the Christian tradition *does* assert (and is the only valid way of meaning “Everything happens for a reason” in the Christian tradition as far as sinful acts goes) is that God wills to turn even our irrational, mysterious, and evil acts to good. As Joseph put it to his brothers after they sinfully sold him into slavery, only for him to wind up as Pharaoh’s Right Hand Man and save his family: “You meant this for evil, but God meant it for good.”
It is the same pattern as the crucifixion and resurrection of Jesus. In that sense only do sinful things happen “for a reason”. But that is not because God wills sin, but to turn our meaningless and stupid sinful choices and acts, done in perverted freedom, to his glory and our good, despite ourselves. In this, the very thing materialism is bound to affirm–“Everything happens for a reason”–is denied by the freedom both of sinners to do things for no reason and of God to insert his free and gratuitous love into the supposedly machine-like working of Creation.
“God has loves, not reasons.” – Robert Farrar Capon