Yes, they're a cult. They also refuse to accept that Jesus is God. They deliberately mistranslate verses that don't support their own twisted theology.

They also shun people who are disfellowshipped. Including their own spouses. Even though the Bible says that you're not to divorce your unbelieving spouse if they consent to live with you.

Blood transfusions are prohibited. They expect you to let your child die rather than get one. They base that on a misinterpretation of the Old Testament law not to eat blood. Yet Jesus said that the Sabbath was created for man, not man for the Sabbath. And Jesus talked about how when David and his companions were hungry they ate consecrated bread that only the priests could eat. God clearly cares more about people than rules.