You explained it better than I..however, the symbolic cross to Christians is certainly not seen as repugnant. I haven't researched this, but IMO, the mormon founder's attitude that the Catholic church was evil and catholics making the "sign of the cross" would probably have something to do with their attitude.
When my father died my best friend, a Temple Mormon, came to the Catholic funeral service. He was obviously a little apprehensive and didn’t know what to expect. As it turned out, there was nothing that gave him grave difficulty and I noticed that he participated in the prayers such as The Lord’s Prayer.