They may truly be sincere. But you must test each doctrine by measuring it up to the Word of God. In the FAQs section under “Cults” you will find the answer to the question, “How can I recognize a cult?” Some guidelines are given and also some questions are listed which you can ask to help determine a religion’s validity.
Many denominations fall under the heading of “Christianity.” Many of them are godly and sound. And many of them, however, err in their doctrines. Countless of those doctrines contain enough error that they are considered heretical but they also contain just enough truth to be attractive resulting always resulting in confusion if you do not know the Word of God.
True Christianity holds that salvation is given by God’s grace and we receive it through our faith. Ephesians 2.8: “For it is by grace you have been saved, through faith-and this is not from yourselves, it is the gift of God.” Furthermore, a true denomination of Christianity points only to Jesus Christ as the way to heaven. Jesus said, “I am the way and the truth and the life. No one comes to the Father except through me” (John 14:6). If someone comes to you trying to convert you to his religion saying anything denies that it is only through Jesus Christ that we can enter heaven, run the other way. They are teaching heresy!