I’m not LDS…but…
As I understand…aren’t baptisms and sealings for the dead done for those people provisionally so that they have the opportunity to CONSENT to their sealings and baptisms in the afterlife?
A child being baptized has no such provisionary consent stated or implied…in baptism and sealings for the dead, the work done for the deceased person does not violate their free will…they can accept or reject the work done on their behalf if they so choose…a child has no such choice.
As I understand the concept of water baptism among Catholics…once a child is baptized there is an indelible mark upon them…they cannot be “un-baptized”…in fact as I understand water baptism…I was part of a discussion on this fourm that a “well-meaning” Catholic COULD baptize a child without the consent of their parents and they STILL would be considered baptized. A Mormon who undergoes baptism by proxy for a deceased person in no way violates the free will of the deceased as they STILL have the choice to accept the efficacy of said baptism or reject it.