Faithful Catholics are the remnant of Jesus’ Church.  We are what St. Paul refers to in Romans 11:2-5:

Do you not know what the scripture says of Elijah, how he pleads with God against Israel? “Lord, they have killed thy prophets, they have demolished thy alters, and I alone am left, and they seek my life.” But what is God’s reply to him? “I have kept for myself seven thousand men who have not bowed the knee to Baal.” So too at the present time there is a remnant, chosen by grace.

It is not enough to say we are Catholics or Christians or “spiritual.”  It is our duty to carry forward the full Truth of Jesus Christ.  That means that we must learn the faith through studying, reading, learning, and teaching all that the Catholic Church declares to be part of the Deposit of Faith.  It is not enough to rely on what we may have learned as children in CCD (or “religious education” or in Catholic schools) or RCIA.  We need to pursue a lifelong journey to know the faith.  We must not be and not remain silent in the face of people who “used to be Catholic” or were “raised Catholic.”  We must proclaim the full teaching of Jesus and His Church – the hard teachings that require people to change their lives as much as any other teachings.