The Savior, like his prophets, will be rejected and spurned because of the lack of vision of those to whom he preaches. The quiet and peaceful truths of heaven are not able to penetrate the hard heart.
Likewise, those with stiff necks are not able or willing to bow the head in humble reverence toward the Lord and those whom he sends in his name.
Those who knowingly have sinned (and wilfully continue in sin) are confronted with the painful reality, humility, and agony of repentance, or the enticing alternative of denial.
Those choosing denial over repentance thereby harden their hearts, stiffen their necks, shun and eventually fight the light of truth, and thus become enemies to God and all righteousness.