But a natural man does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually appraised.
(1 Corinthians 2:14)
It can be frustrating sharing biblical truth with an unbeliever. As someone has said, "Don't try to teach a pig to sing. You will get frustrated and the pig will get irritated!" Jesus said,"Do not give what is holy to dogs, and do not throw your pearls before swine, or they will trample them under their feet, and turn and tear you to pieces."(Matthew 7:6)
The problem, of course, is that the things of the Spirit of God, including the word of God, are spiritually appraised or spiritually explained. The natural man or unbeliever does not have the spiritual discernment to understand, let alone, trust and obey the truth of God's word. But Christian believers have the Holy Spirit who illuminates Scripture and empowers us to understand, believe, trust and obey God's word; But he who is spiritual appraises all things, yet he himself is appraised by no one. For who has known the mind of the Lord, that he will instruct Him? But we have the mind of Christ. (1 Corinthians 2: 15, 16)
Frustrating or not, we must still proclaim the Gospel of Jesus Christ to unbelievers and pray that, if it is His will, God will mercifully give them the spiritual ears to hear and the spiritual eyes to see His truth. However, it is futile and throwing your pearls before swine when we try to get unbelievers to be more like Christ. Yes, proclaim the good news of Jesus Christ to anyone who will listen and praise and thank God that you do indeed have the mind of Christ. To Him be the glory! Maranatha!