Can we call a group which is not organized, a body? No! The term itself, "BODY" means an organization. Remember that a body is an organizatino of body-parts, in which the body-parts are joined and knit together by joints:

16 from whom the whole body, joined and knit together by what every joint supplies, according to the effective working by which every part does its share, causes growth of the body for the edifying of itself in love. (Ephesians 4:16, ibid)

Can we call a group of men with their own belief which is different and contradictory to each other, a body? No! We should not forget that a body has only one head. And the head of the body of Christ is Christ Himself:

18 And He is the head of the body, the church, who is the beginning, the firstborn from the dead, that in all things He may have the preeminence. (Colossians 1:18, ibid)

Since there is only one head, then a body should receive one kind of signal or instructions which is the signal coming from its head. In other words, this one body has only one spirit just like what Apostle Paul said:

4 There is one body and one Spirit, just as you were called in one hope of your calling; (Ephesians 4:4, ibid)

And is it true that Church affiliation has nothing to do with Salvation? No! In fact Christ told us that those who will enter by Him are only those who will be saved:

9 I am the door. If anyone enters by Me, he will be saved, and will go in and out and find pasture. (John 10:9, ibid)

Entering Christ means joining his body as members of it.

4 For as we have many members in one body, but all the members do not have the same function, 5 so we, being many, are one body in Christ, and individually members of one another. (Romans 12:4-5, ibid)