Gospel Deniers Are Unregenerate

"Who is a liar but he who denies that Jesus is the Christ? He is antichrist who denies the Father and the Son. Whoever denies the Son does not have the Father either; he who acknowledges the Son has the Father also."  (I John 2: 22-23)

Denying Christ, failing to believe in him, makes one a liar and "all liars" and unbelievers will have their part in the lake which burns with fire and brimstone. (Rev. 21: 8) Those who deny Christ and the Father are antichrists and have neither the Father nor the Son. Only those who believe in Christ, who believe "the record that God has given of his Son" (I John 5: 10), who "acknowledge" both the Father and the Son, are saved people. 

This uproots the Hardshell idea that heathens "have" the Father, Christ the Son, and the Spirit. The heathen are they who deny the Father and the Son. How then can Hardshells affirm that Muslims, Buddhists, Hindus, etc. are saved even though they deny and do not acknowledge Christ and the Father?