Answer:
People who are angered at members of the Church of Jesus Christ of Latter Day Saints (commonly called "Mormons") have many reasons. Some are angered or offended by their conservative moral standards and support for conservative moral ideals, as in the recent gay marriage backlash. Others, mostly evangelical and born-again Christians, are angered about their religious doctrines and picket Mormon buildings. Some are angry when the Church proposes building a new meetinghouse or temple in their neighborhood, as is currently the case in Phoenix, Arizona. Others feel that Mormons are a cult, anti-Christian, oppressive, etc and take out their feelings by vandalizing meetinghouses.
Many of those who are angry with the Church or it's members are uninformed. Church leadership usually responds to current events at http://newsroom.lds.org to inform the public as much as possible of their stance on current controversial issues.