How do we know? Because it militates against the very purposes Jesus said represented His Father: 17For God did not send his Son into the world to condemn the world, but to save the world through him. (John 3:17)
Anybody reading about the Book of Mormon jesus having an anger fit upon dying, smoting 70,000 - 90,000 people with fiery, watery, and earthy deaths - would have to proclaim John/Jesus re: John 3:17 words as "lyin'" words!
You are on a roll today, Brother!
Praise God!
Consider what had happened to Jesus immediately prior - the nation of Israel rejected Him and cruxified Him. Did Jesus vent death and destruction of Jerusalem upon His resurrection - certainly they deserved it, they had heard his very voice. Yet while on the cross Jesus said "Father, forgive them for they know not what they do" Yet to an alledged peoples who hadn't heard his voice, he arrives by killing tens of thousands. That's not my King, thats not my Jesus.