LDS - Sealing a family member after he/she dies?

My father's side of my family is LDS and I am not. I'm spiritual but do not belong (and do not want to belong) to a church. They've mentioned in the past that the church can baptize and seal its member's family members postmortem. I wonder though, what about people who do not want this if they were to die before their parents (or other close family members who are LDS)? Isn't this practice selfish, considering the living aren't able to get the consent of the dead, but have the option to follow through on this postmortem baptism and sealing anyway? I feel like it's an invasion of privacy and autonomy, for lack of better words. How does the church reconcile this conflict?