Actually, Mormonism doesn't teach that grace saves.
That just isn't true. It's by God's grace anyone will obtain eternal life.
It's grace + works, which nullifies the grace.
So--was God's grace nullified here?
Acts 2:38-42---King James Version
38 Then Peter said unto them,
Repent, and be baptized every one of you in the name of Jesus Christ
for the remission of sins, and ye shall receive the gift of the Holy Ghost.
39 For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.
40 And with many other words did he testify and exhort, saying, Save yourselves from this untoward generation.
41 Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls.
42 And they continued stedfastly in the apostles' doctrine and fellowship, and in breaking of bread, and in prayers.
Matthew 19:16-19---King James Version
16 And, behold, one came and said unto him, Good Master, what good thing shall I do, that I may have eternal life?
17 And he said unto him, Why callest thou me good? there is none good but one, that is, God:
but if thou wilt enter into life, keep the commandments.
18 He saith unto him, Which? Jesus said, Thou shalt do no murder, Thou shalt not commit adultery, Thou shalt not steal, Thou shalt not bear false witness,
19 Honour thy father and thy mother: and, Thou shalt love thy neighbour as thyself.
First, as usual, you dishonestly quote Bible verses out of context. That's not even remotely the whole thing.
That's seems to be the usual claim of those whose theology is violated by the scriptures, IMO.
Second, Paul is contrasting Adam and Christ. He is saying that Christ is the propitiation for sin for all men, not that all men will partake it it or be saved.
I've never made any claim all men will be saved unto life. All men are absolved of the condemnation of the Fall--and thereby, all have the opportunity to inherit eternal life, as a free gift to all men:
Romans 5:18---King James Version
18 Therefore as by the offence of
one judgment came upon all men to condemnation; even so by the righteousness of one
the free gift came upon all men unto justification of life.
It's referred to as the Redemption.