The virgin birth is an absolute Truth and is necessary if Jesus is God Incarnate. For if Jesus had two human parents — was the product of human reproduction — then He did not pre-exist, and was therefore not God. It would mean He was born OF this world.
Every human being since Adam has been born OF this world. But Jesus continually claimed that He CAME INTO this world from the outside, He is the only person to ever be born into this world from the outside. This required a virgin birth so that He His life could be supernaturally implanted into Mary’s womb – thus maintaining His identity, individuality, and divinity. Thus, those who deny the virgin birth are denying that Jesus was God, denying the Bible, and calling Jesus a liar. It is just that serious.
To deny the virgin birth is to deny GOD BECAME MAN. But this, in turn, is an actual denial of Jesus as Savior, and thus, of the redemption He accomplished. Only if Jesus was God become man, and lived a sinless life, could He bear the sin of the world, and be the Savior.
Someone once said that those who deny the identity of Christ usually always deny at least the two Truths of the virgin birth and the resurrection. These two Truths are essential to the identity of Jesus of God, and thus, make us accountable to Him.