I ve observed several barriers. The most serious is that they saw Christians failing to live an authentic Christian life. They showed little Christlike love in their relationships or in their family lives. Especially, they displayed little love or care in their workplace, where it really would have showed and counted. The unbeliever expected to see love and could not understand a true Christian not being a loving person.
Sin is a serious hindrance.
A Christian who practices sin before a watching world is a great hindrance to a non-Christian. This is especially true in the workplace. When church members refuse to love one another, and a church is divided, people are greatly hindered in coming to know Christ. This is often true of unsaved family members. When they see Christians in a church argue, gossip or harbor racial prejudices, they wonder about the validity of what is said about Christ.