I know a few people today who I would call, "lone ranger" Christians. They like Christ, but not the Church. They are opposed to "institutional" Christianity. They would rather be by themselves, and not in attendance at a local congregation. It's just them, their bibles, and the Holy Spirit.
However, I think that not only is this a dangerous position to be in, but also a denial of what Christianity is.
The Latin phrase "Extra Ecclesiam nulla salus" means: "Outside the Church there is no salvation". The Catholic Catechism on this issue rightly says, "all salvation comes from Christ the Head through the Church which is his Body." This expression comes from the writings of Saint Cyprian of Carthage, a bishop of the 3rd century. The Eastern Orthodox, the Roman Catholics, and the Protestants all agree with this statement.
An prominent Eastern Orthodox bishop, Kallistos Ware, has expressed this teaching as follows:
"Extra Ecclesiam nulla salus. All the categorical strength and point of this aphorism lies in its tautology. Outside the Church there is no salvation, because salvation is the Church" (G. Florovsky, "Sobornost: the Catholicity of the Church", in The Church of God, p. 53). Does it therefore follow that anyone who is not visibly within the Church is necessarily damned? Of course not; still less does it follow that everyone who is visibly within the Church is necessarily saved. As Augustine wisely remarked: "How many sheep there are without, how many wolves within!" (Homilies on John, 45, 12) While there is no division between a "visible" and an "invisible Church", yet there may be members of the Church who are not visibly such, but whose membership is known to God alone. If anyone is saved, he must in some sense be a member of the Church; in what sense, we cannot always say."
Martin Luther said on this subject:
"Therefore he who would find Christ must first find the Church. How should we know where Christ and his faith were, if we did not know where his believers are? And he who would know anything of Christ must not trust himself nor build a bridge to heaven by his own reason; but he must go to the Church, attend and ask her. Now the Church is not wood and stone, but the company of believing people; one must hold to them, and see how they believe, live and teach; they surely have Christ in their midst. For outside of the Christian church there is no truth, no Christ, no salvation."
John Calvin, in the Institutes of the Christian Religion said, "beyond the pale of the Church no forgiveness of sins, no salvation, can be hoped for". Calvin wrote also that "those to whom God is a Father, the Church must also be a mother."
The idea is further affirmed in the Westminster and London Baptist Confessions of Faith that "the visible Church is the Kingdom of the Lord Jesus Christ, the house and family of God, out of which there is no ordinary possibility of salvation."