Galatians 1:8, But even if we or an angel from Heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed.
The apostles, commissioned by Christ’s authority to baptise and teach with the direction of the Holy Spirit, have handed down to the Church the pure Gospel. Any who preach a gospel other than Christ crucified is, therefore, cursed: Mormons, Jehovah’s Witnesses, Muslims, Buddhists, Hindus, Joel Osteen adherents, and any other who reject Christ crucified as proclaimed in apostolic doctrine. This harsh word of the Law must be preached in our pluralistic culture, for Christ has made indubitable that He is the only way (John 14:6). As such, our pluralistic culture is intentionally antagonistic towards Christianity, for they all want to devise their own way and frame their own gods, as is the archaic pagan way. Some Christians, as a result, have grown weak in the face of this adversity and thus approve false gospels. Others conform to them or even fall away completely. Let this harsh word of the Law, therefore, be known and with it the proclamation of Christ crucified for all, even for those deceived by false gospels. Let us who have this pure Gospel be meek, patient, and compassionate towards the deceived, for we too were once estranged from God, but Christ reconciled us to God by His body and blood in order to make us blameless before God (Colossians 1:22-23).
The Lutheran Column 