I have multiple reactions to this Mormon practice of posthumous baptisms of strangers. Temple baptism rites performed for Obama's mother in Provo LDS temple
On the one hand, to try and change someone's religion after their death is an astounding act of hubris. "We know so much better than you," such an act says, "that we will change your religion after death." Moreover, God will let them? How does that work? According to Church doctrine, per the article: "The Church does not list persons as members of the Church or 'Mormons' merely because proxy baptisms have been performed. Church doctrine teaches that at some point the spirit of the deceased person will be informed that a baptism has been performed on his or her behalf and will be given the opportunity to accept or reject it." So, the damned are screaming in some pit somewhere and someone walks up and says "hi! you've received a proxy baptism!...." It's like some bizarre encyclopedia salesman skit.
On the other hand, it's cowardly. If you can't convince someone to join your religion during their lifetime, you go behind their back? How is that doing unto others, for that matter?
Finally, but most importantly...it's really meaningless. If someone proxy baptizes me after I'm dead, I haven't done anything to change religion, so as offensive as it sounds, nothings really changed, has it?