The Onion couldn't have made up a better headline. Apparently, Mormons have this practice where they will posthumously baptize your ancestors in order to let you be a Mormon. Even more crazy is that this arbitrary practice really pisses of Jews whose ancestors were killed by the Nazis because they were Jewish.

If you are Jewish, you don't believe Jesus was who Christians say he was. So, from the Jewish perspective, Mormons are just making shit up when they go to church and marry a bunch of 12 year old wives. That should also mean that if they "baptize" your Jewish grandmother in name only (they're not digging up mass graves at Auschwitz), they might as well be casting a Harry Potter spell on them from 3000 miles away - i.e. it is meaningless.