http://www.sltrib.com/home/3505422-155/mormon-church-opposing-utah-medical-marijuana?fullpage=1I tried to cut it down far enough to avoid copyright issues, but wanted to leave a lot in to explain the issue at stake.
In any case, speaking as a Mormon, this isn't surprising. The church generally weighs in on issues it considers moral issues, which usually includes LGBT issues and alcohol laws. This time, medical marijuana actually has a chance of passing, so the LDS Church wants to keep that from happening, as they have with other mind-altering substance issues.
What's interesting is that they publicly have no comment on the other medical marijuana-related bill, which is much more limited, but still legalizes it to a certain extent. The "no comment" on one bill with a strong condemnation of the other implies support for the limited bill. So the Church seems to have abandoned banning it altogether, but would support extremely limited medical marijuana (I.e, no smoking it, but in favor of gels, oils, that sort of thing).