D&C 124:29-30; “For a baptismal font there is not upon the earth, that they, my saints, may be baptized for those who are dead—For this ordinance belongeth to my house, and cannot be acceptable to me, only in the days of your poverty, wherein ye are not able to build a house unto me.”

1 Cor. 15:29; “Else what shall they do which are baptized for the dead, if the dead rise not at all? why are they then baptized for the dead?”

Temples in the NT era are not made with hands and baptizing dead people is necromancy.

Baptisms for the Dead

Ensign, April 2002, pg. 4; “What a marvelous thing that is that you, an ordinary boy or girl, can stand in the place of some great man or woman who at one time lived upon the earth but who is now powerless to move forward without the blessing that you can give to him or her. … There is no greater blessing that you can have than to stand as a proxy in a great service to those who have gone beyond. And it will be your privilege and your opportunity and your responsibility to live worthy to go to the temple of the Lord and there be baptized in behalf of someone else.”
— Gordon B. Hinckley

Leviticus 18:21; “And thou shalt not let any of thy seed pass through the fire to Molech, neither shalt thou profane the name of thy God: I am the LORD.”

No one except for the Creator of mankind can decide where man goes.  The only person who’s stood in the place for others is Jesus when He hung on that cross for all of us.