Mormons ARE monotheists: we believe in the Father, the Son, and the Holy Spirit, 3 individuals whom are 1 God united in will/purpose/perfection (as opposed the Trinitarian united via co-substantiation). In the Mormon view, this is still completely monotheistic because to worship the Father is to worship the Son because they are completely united. To follow the Son’s commandments is to follow the Father’s commandments. This view is supported in scripture: where husbands and wives are commanded to be one, we are also commanded to one with each other, and Jesus sacrifice enables us to (after repentance and perfection) be one with God.