"Homosexuality is wrong. If no one ever tells these people that, won't they continue to think it's okay?"
Even as I wrote those words I was thinking there is a part within every human being that knows when he or she is doing wrong. We may ignore it. We may tell it to be quiet in order to make it go away. And if we do that often enough for long enough, we can successfully silence it. But it is still there.
It is as if each incident of ignoring or silencing that voice within burns that spot within us that is sensitive to the sin. If that sensitivity is burned enough, it will lose sensation.
Did you know that a third degree burn doesn't cause pain? A first degree burn turns the skin red and is painful. A second degree burn is red with blisters and is very painful. A third degree burn is black and charred and produces no pain because the nerves have been burned and destroyed.
The good news is that if a person wants to restore that part of him- or herself that whispers to our minds when something is wrong, it can be restored. God can heal the seared conscious and restore its sensitivity.
"...the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts now accusing, now even defending them."
Romans 2:15, NIV