Are all church members true Christians? No. One may be a member of any church, yet not be "in Christ." Union with Christ is what makes the true Christian, nothing less. One may be a zealous churchman, an ardent worker for a denomination, an active officeholder in a Christian group, earnestly seeking the good of the "Cause." Yet that one may be "without Christ," and, therefore, not a Christian, or "Christ one," as the Bible uses the name.
Where church membership is open to all who are not guilty of flagrant sin—and, sad to say, some who are—it is not to be wondered at if persons who have not been born of God, who have no vital union with Christ, who have no personal reliance on His precious blood, and no knowledge of their salvation, "creep in unawares." They may have become communicants wholly apart from personal dealing with God and heart acceptance of His Son as Savior, Redeemer and Lord.
How solemn it is to act so! And what an awful judgment awaits those who encourage others whom they know to be unfit, to come to the Lord's Table, and there profess to be what most of them know that they are not.
No "membership" in any church makes a Christian. Nor does church "connection" secure a place in heaven for anyone.
The gospel is God's good news of a Savior provided and a salvation proclaimed to all. Those who receive that Savior by faith, and are "in Christ" and He in them, are Christians—nobody else.
Some who are truly born of God may not always glorify their Father in heaven. They may at times conduct themselves carelessly, and in their ways become like to "the world of the ungodly," thus bringing divine chastisement on themselves and dishonor on the name of the Lord. But this does not change their relation to God as Father, or to Christ as Lord. Because they "belong to Christ" they will be made to feel their backsliding. God must chastise His erring child in order to restore him to walk in "the paths of righteousness.”
But the false professor, he who has no possession of Christ; the one who has "a name to live," but has no spiritual life; who is "in the church," but not "in Christ," must, sooner or later, now or in the coming judgment, be stripped of his false profession. His hypocrisy must be exposed, and the unreality of his life, as God knows it, shall be laid bare.
"For God shall bring every work into judgment, with every secret thing, whether it be good, or whether it be evil." Eccl. 12:14.
Reader, make sure your Christianity is of God, and it will be real.