The problem with discussing theology with with pseudo-Christians is that they use the same words, but with different meanings. Mormonism, for example, still teaches that salvation is by grace. The problem is that Mormons have a very different idea about what that means. Whereas the Bible clearly says we are saved by grace, through faith, not of ourselves because it is the gift of God, and not through works (Ephesians 2:8-9), Mormonism has its own version of this verse in the form of 2 Nephi 25:23. But rather of saying "not of works, lest anyone should boast", the Mormon version says we are saved by grace after all we can do.
As if Ephesians 2:8-10 wasn't clear enough, Romans 11:6 seals the deal by telling us that grace and works are mutually exclusive. If you are saved by grace, it is no longer of works, otherwise grace ceases to be grace. And if salvation is of works, then it is no longer of grace, otherwise work is no longer work. In other words, you simply cannot accept the Mormon definition of grace if you believe the Bible, because the Bible explicitly defines grace and works as being separate. It is linguistically impossible to say that grace and works both play a part in our salvation. That's not to say people don't try, but thankfully, the Lord saw fit to prevent them from succeeding.
Mormons need to know that when their Church teaches that salvation is by grace, it is telling the truth, but the great news is, this isn't "after all we can do", any more than a mansion is free "after all you can pay". Grace and works are antithetical. The grace we receive from God is that although our works merit eternity in Hell, Jesus' works were pristine, yet He died as if He was a sinner. Because He, being perfectly righteous, died as a sinner, we, who are sinners, can live eternally as if we were righteous.