Replies

There is a tendency however for some to exclude all who do not believe exactly the same way as they do, as not being members of the body.

I did not start it, St. Paul did:

11 ...there are contentions among you. 12 Now this I say, that every one of you saith: I indeed am of Paul; and I am of Apollo; and I am of Cephas; and I of Christ. 13 Is Christ divided?
(1 Cor 1)

Adherence to theologies of men, such as Luther or Calvin, disqualifies as membership in the Church of Christ, despite professions of His name, inasmuch as they differ from the teachings of the apostles.

Not every one that saith to me, Lord, Lord, shall enter into the kingdom of heaven: but he that doth the will of my Father who is in heaven, he shall enter into the kingdom of heaven
(Mt 7).

Thank you, annalex! The Paul v Apollos dispute (which should not be a dispute) underscores exactly what I was saying:

And I, brethren, could not speak unto you as unto spiritual, but as unto carnal, [even] as unto babes in Christ.

I have fed you with milk, and not with meat: for hitherto ye were not able [to bear it], neither yet now are ye able.

For ye are yet carnal: for whereas [there is] among you envying, and strife, and divisions, are ye not carnal, and walk as men?

For while one saith, I am of Paul; and another, I [am] of Apollos; are ye not carnal? Who then is Paul, and who [is] Apollos, but ministers by whom ye believed, even as the Lord gave to every man?

I have planted, Apollos watered; but God gave the increase.

So then neither is he that planteth any thing, neither he that watereth; but God that giveth the increase. – I Cor 3:1-7