This article is my best guess as to why they picketed: "Unfortunately, Nimoy’s high level of fame and his large and loyal following made him an ideal target for the Westboro Baptist Church, a group that pickets funerals of soldiers and anyone with a high profile. The Westboro Baptist Church associated their picket threat with other Star Trek stars, and the things about those stars that the group opposes: George Takei and Zachary Quinto, who are openly gay (the WBC’s favorite conversation piece), and William Shatner, who the Westboro Baptist Church claims “hates God.”
http://www.inquisitr.com/1881975/wes...imoys-funeral/