The Watchtower Bible and Tract Society (the Jehovah’s Witnesses) was founded by Charles Taze Russell. Russell was raised in a Presbyterian (Calvinist) home until he was 13 years old and then joined a Congregational Church. At age 16, he began to seriously question Christian orthodoxy and became caught up in the Adventist movement which led to his founding what is now commonly known as the Bible Student movement. He was never a Mormon, and the Watch Tower Bible and Tract Society was NEVER even remotely Mormon in its theology.
Calvinism is NOT a cult.
From the Merriam-Webster Online Dictionary:
cult
noun, often attributive \ˈkəlt\
: a small religious group that is not part of a larger and more accepted religion and that has beliefs regarded by many people as extreme or dangerous
: a situation in which people admire and care about something or someone very much or too much
: a small group of very devoted supporters or fans
Full Definition of CULT
1
: formal religious veneration : WORSHIP
2
: a system of religious beliefs and ritual; also : its body of adherents
3
: a religion regarded as unorthodox or spurious; also : its body of adherents
4
: a system for the cure of disease based on dogma set forth by its promulgator <health cults>
5
a : great devotion to a person, idea, object, movement, or work (as a film or book); especially : such devotion regarded as a literary or intellectual fad
b : the object of such devotion
c : a usually small group of people characterized by such devotion