It is true, that Paul in the scripture (Romans 14, 1Corinthians 8, etc.) spoke of different measures of faith and God wants those with greater faith to receive those with lesser faith with love and should not despise them. This is the unity of the family of Christ.
However, I have seen those who teach the "unity of Christians" to those with lesser faith that it is those with greater faith who has lesser faith and to have "sympathy" on them who are actually greater in faith.
This kind of perversion prevents the church from further growing in knowledge of Christ and causes a fake unity, making deceitful witness before the grace of God.
These false teachers will have serious judgment from God when the time comes.