I’m going to take the liberty of paraphrasing a passage from the book of Mormon. If you dispute this passage in the book of Mormon I guess I’ll have to try to find the reference and quote it exactly, but here’s the paraphrase:
There are save two churches only, one is the church of God and the other is the church of the devil. And whosoever does not belong to the church of God belongs to the church of the devil.
JohnVIII,
You have a good memory. That is a very important verse. Add to that the verses in Moroni 7 that say as follows:
10 Wherefore, a man being evil cannot do that which is good; neither will he give a good gift.
11 For behold, a bitter fountain cannot bring forth good water; neither can a good fountain bring forth bitter water; wherefore, a man being a servant of the devil cannot follow Christ; and if he follow Christ he cannot be a servant of the devil.
12 Wherefore, all things which are good cometh of God; and that which is evil cometh of the devil; for the devil is an enemy unto God, and fighteth against him continually, and inviteth and enticeth to sin, and to do that which is evil continually.
13 But behold, that which is of God inviteth and enticeth to do good continually; wherefore, every thing which inviteth and enticeth to do good, and to love God, and to serve him, is inspired of God.
14 Wherefore, take heed, my beloved brethren, that ye do not judge that which is evil to be of God, or that which is good and of God to be of the devil.
15 For behold, my brethren, it is given unto you to judge, that ye may know good from evil; and the way to judge is as plain, that ye may know with a perfect knowledge, as the daylight is from the dark night.
16 For behold, the Spirit of Christ is given to every man, that he may know good from evil; wherefore, I show unto you the way to judge; for every thing which inviteth to do good, and to persuade to believe in Christ, is sent forth by the power and gift of Christ; wherefore ye may know with a perfect knowledge it is of God.
17 But whatsoever thing persuadeth men to do evil, and believe not in Christ, and deny him, and serve not God, then ye may know with a perfect knowledge it is of the devil; for after this manner doth the devil work, for he persuadeth no man to do good, no, not one; neither do his angels; neither do they who subject themselves unto him.
What counts is what is in the heart of each person, as I said before. Each person decides which “church” they belong to, and they show it by what they do–whether they follow the light of Christ by doing good things and by not judging harshly. This is very important. I have no idea whether every Catholic in the world is following the light of Christ, but I think many, perhaps most, perhaps nearly all are, so the other verse you cited would say that Nephi is saying they “belong to the church of the Lamb of God.” Each one decides by how they live.
Please understand this. Peace to you.