Their own words about the religion contradict your claims.
He is the head, the only sure foundation and cornerstone upon which to build.
Christ, the Creator God, the "I AM, the Alpha and the Omega, the first and the last, the beginning and the end" (Revelation 22:13), most certainly is the only sure foundation and cornerstone; "I AM the Way, the Truth, and the Life" (John 14:6).
Colossians 1:
14 in whom we have redemption through His blood,the forgiveness of sins.
15 He is the image of the invisible God, the firstborn over all creation.
16 For by Him all things were created that are in heaven and that are on earth, visible and invisible, whether thrones or dominions or principalities or powers. All things were created through Him and for Him.
17 And He is before all things, and in Him all things consist.
18 And He is the head of the body, the church, who is the beginning, the firstborn from the dead, that in all things He may have the preeminence.
Modern ‘Christians’ haven’t tarred and feathered, murdered, stolen property or other horrible things to Mormons in a long time.
I see no problem with reaching out to enlightened Christians today. We all could learn from each other.