They can't, John, because they can't see it. They are spiritually blind to the truth of God's word and instead seek their own opinions over His. Until the Lord removes the blinders, we are unable to see Him as He is or respond to Him with the gift of faith He planted in us (John 9, Ephesians 2). Ultimately, it's 100% God and 0% us in salvation.
So can a leopard change his spots? Absolutely not. But with God, all things are possible. He can change them.
Another denomination pushed to the brink of extinction by pervasive liberalism and Progressive stances. They are asking what they can do. He story ends with an apology to the LGBT community for not supporting homosexual marriage as a body after a vote over the summer failed to garner sufficient support.
Repenting of actual sins defined by the Lord they claim to follow and uphold would be the best start. They do need to say they are sorry, but they need to say "sorry" to God first and foremost for supporting things He abhors.