I have always thought of a cult as an organization that started with the often extreme beliefs of one person, followers had to agree with everything with no freedom of expression, they have control over your life, and it is very hard to leave.
The witness argument that it wasn't a cult was always 'Because Russell simply used the bible to seek out truths!' All you have to do is read his old books to see he didn't simply use the Bible. He used the pyramids of Egypt. He used his own many, many strange thoughts. The religion splintered and Rutherford took over one faction and made the religion a police state which became the JW's we know today. You leave, you lose your family. That's only an extremist Muslim thing, and a cult thing (scientologists, JW's). Really. That is NOT normal.