By most definitions, a Christian is someone who accepts Jesus Christ as their Lord and Savior. If a Mormon does that, by definition they are Saved. If you want to change the definition, it’s fine with me.
“The main one being that Mormons do not believe in the Trinity”
You are assuming that every Mormon doesn’t believe in the trinity. I think you are confusing Mormons with Mormonism. The LDS church is not Trinitarian. The only Mormon I ever asked about it said he believed in the Trinity.
If a person is a Mormon, then they are identifying with all the beliefs and pronouncement of the LDS belief system.
Even if they are ignorant of them.
Therefore, when a Mormon "accepts Jesus Christ as their Lord and Savior" they are accepting the Mormon Jesus, not the Biblical Jesus.
If they are accepting the Biblical Jesus, they cannot be a Mormon.
The Biblical Jesus is not the brother of Satan. The LDS jesus is.
The Biblical Jesus was conceived via the Holy Spirit, the Mormon jesus was conceived by a physical act between the Mormon god of this world (referred to as Heavenly Father) and Mary, the mother of the Biblical Jesus.
That is from their set-in-stone LDS writings.
Pretty sure he's still a Trinitarian though.
Even Catholics have a hard time believing in the Trinity. The best we can do is to treat it as a MYSTERY and just accept it. They cannot explain it, or so I was told by the priest who gave me my convert classes.
I'll bet not very loudly!
I'll bet he was a NEW mormon convert that had been a nominal, lacking in KNOWLEDGE 'christian'; or a 'mormon' soon to be out of the yawning maw of MORMONism.