**Mormonism is not Christianity, and neither is Catholicism, or Islam, or many other false religions born in the pit of hell. One of Satan’s big schticks is to create false “religions” to deceive billions of people.**
That’s being honest; a little bit ‘cart before the horse’, but honest. It’s best to present at least some of your opinion with scriptural harmony, all the while being ‘wise as serpents and harmless as doves’.
Yes, you’re right, but I can cite Scripture all day, and those who are locked in deception, whether Catholicism, Mormonism or whatever, will not be convinced. In the same way that sick, twisted maniac Fred Phelps uses Scripture to support his lies born in the pit of hell, so false religions also use Scripture to justify their false teachings and beliefs.
I could point to Galations, Chapter 1, verses 6 through 12, where Paul warns of false “gospels” which pervert the gospel of Christ. Or, I could mention the last chapter of Revelation, in verses 18 and 19, where John warns of adding to or removing from the Word of God. I could cite the passages in Revelation 13, 18, 19 and 20 dealing with the deception by the devil, the beast and the false prophet of “all nations” and “them that dwell on the earth,” but I would not likely sway a single Catholic or Mormon.