Rejection of the sacrament is basically what it is. It's hard to define someone as a Christian who willfully denies both the divine nature of Jesus AND does not take part in the "body" and "blood". I am saying this as someone who is not a christian, but looking from the outside in. There has to be some way to define a person of religion. With that in mind, I don't think you can call JW's Christian at all. If anything they are antichristian, and have a belief system that seems to have more in common with the Dualistic spiritual struggles of Zoroastrianism, with a bit of doomsday cult gingerbread tacked on.