With Mitt Romney again running for President of the United States, the word "cult" is getting a lot of air time.
Is the Mormon church a cult? You can't give a simple yes or no answer.
There are (at least) three ways to use the word "cult" — and they're all correct usage:
The broadest, but least common, refers to any system of worship. It is not derogatory; it simply distinguishes one religious group from another. In history, the "Jewish temple cult" was the way orthodox Israelites worshipped YHWH at Solomon's temple in Jerusalem.
The narrowest, and most common among Americans at large, refers to groups with wildly unusual teachings that influence their members using unethical tactics (e.g., sleep deprivation) and try to cut them off from their friends and families (at least in the popular imagination). Think Branch Davidians or Heaven's Gate.
In between these two in scope is a usage that is common among American Evangelicals: a group that is an unorthodox off-shoot of an existing religion. It simply refers to groups that don't follow all of the rules. By this definition Christianity is a cult of Judaism, and the Jehovah's Witnesses are a cult of Christianity (because they do not hold to the deity of Christ or the doctrine of the Trinity).
The Church of Jesus Christ of Latter-day Saints (aka, LDS Church or Mormons) is also a cult of Christianity by this definition.
The problem is that most Americans, when hearing the word cult, think about David Koresh or Jim Jones. To these Americans, calling the Mormon church a cult is sure sign that you are a weirdo. You'll rarely, if ever, be given a chance to explain what you mean. You'll simply be tuned out or castigated.
It is not useful to call the LDS Church a cult in politics or apologetics. It demeans you. Just don't do it.