I find it hard to get upset about “posthumous baptisms” by Mormons of Jews, whether Holocaust victims or otherwise.
Either the Mormons are right about their theology, or they’re wrong. If they’re right, then the posthumous baptism will do good. If they’re wrong (and, being not a Mormon, I by definition think they are wrong, or else I’d be a Mormon), then the baptism will have no effect whatsoever: It is just some people going through some ineffectual — by hypothesis — rituals in their own temple, and I don’t see what it should be to me that those rituals use the names of (say) my late relatives, however much I love those relatives.
I suppose if someone’s theology was that Mormon baptisms did have metaphysical effect, but a bad effect (e.g., made the subject go to Hell), then that person would understandably object to those baptisms. But as best I can tell, that’s not Jewish theology — the Jewish religious view is that those rituals have absolutely no consequence, temporal or spiritual.
Nor do I see anything particular ill-mannered about this. True, the baptisms rest on a certain form of arrogance: The Mormons think they know God’s will better than others do, and think that it’s better for a soul to be baptized Mormon rather than to remain Jewish (assuming for purposes of discussion that such a statement can make sense). But that isn’t much different from the normal view of most religious people that their religious view is right and those that disagree with it are wrong — and, again, it’s a sort of arrogance that has no practical effect on anyone, living or dead, other than the Mormons themselves.
Now apparently Mormon authorities had said they wouldn’t do this [UPDATE: though some say no such promise was made], so one could fault them simply for breaking their promise. But given that the promise [UPDATE: if there is one] is about something that’s so inconsequential, I don’t see why we should be that terribly upset about this. If the Mormons want to remotely baptize my soul or my ancestors’ souls, they can feel free to do so — I just don’t see what it could possibly mean to me or to my loved ones.