The bible teaches of those who rejected the truth so often, they are sealed to it and can never accept it. It is like cauterizing a wound, the action while painful immediately, kills the very nerves that would feel the pain leaving that particular area unable to sense pain in the future. The bible calls it 'searing ones consious'.
Another way of looking at it is if one tells a lie often enough, even they themselves will believe it to be the truth.
When a person spends a lot of time dwelling on one particular subject, pretty soon, they become unable to think on others. Persons or peoples who spend their lifetimes hearing hatred will soon join in and begin spreading the same hatred, they will be controlled, (perhaps possessed), by it.
A lifetime of rejecting the one true God leaves nothing but Satanic influences left until they die and face the judgement of God for their lives.