Christianity is not based on fear. It is based on the person and work of Jesus Christ. The whole foundation of Christian theology rests on the person of Christ who, according to the Scriptures, is God in flesh (John 1:1, 14), who bore our sins in his body on the cross (1 Peter 2:24), and who died and rose from the dead three days later (1 Corinthians 15:1-4).
However, there is nothing wrong with being motivated to become a Christian based on trying to avoid the righteous judgment of God. In such a case, fear is properly warranted and wisdom would dictate the necessity of avoiding God's judgment. If that judgment scares people and motivates them to come to Christ and be forgiven of their sins, then that is a good thing.
But, what motivates one person may not motivate another. One person may want to become a Christian because of fear, where another might be motivated out of love for God, or sorrow for sin, or fatigue due to the consequences of rebellion against God. People's reasons for becoming believers can vary wildly, but the fact is that Christianity is not based on fear. It is based on God's work through Jesus to bring people into salvation. Fear is a proper motivator when accompanied by wisdom.
- Prov. 9:10, "The fear of the Lord is the beginning of wisdom..."
- Matt. 10:28, "And do not fear those who kill the body, but are unable to kill the soul; but rather fear Him who is able to destroy both soul and body in hell."
Let's take, for a moment, the issue of Christianity being based on fear according to the Scriptures listed above. If a critic wants to complain about this "fear," then on what basis does he or she complain? Is it his opinion, or is there a universal standard to which he appeals? Is he saying that fearing God is a bad thing? If so, why? Why would it be morally wrong to fear the infinite God of the universe and his holy and righteous judgment? By what standard does a critic assert that such fear is not wise or proper? After all, is it not smart to fear the judge and appeal to his mercy before sentencing?
So, Christianity is not based on fear, but fearing God is a logical as well as wise thing to do because God is the judge who has the right to execute lawful and moral judgments upon sinners.