Why Do Jehovah witnesses insist that Jesus' Body was destroyed?

I'm not a JW but if you do away with the bodily resurrection from the grave [tomb] of Jesus, then, the crux of Christianity is dead too. What future would there be for Christians or for any human being from Adam forward, should the body of Christ been destroyed? If Christ's body were destroyed then, we have no hope for a resurrection, ourselves - do we? This is ample proof that JWs are most definitely a CULT !