Jehovah's Witnesses, do you believe 1 Thess 5:21?

Why can't you understand that the majority of us used to be religious members of Christendom ? It was the Jehovah's Witnesses teachings with the Bible that freed us from the spiritual darkness that we used to be in.And now we are helping others to do the same. We already know everything about what Christendom believes. And it makes no sense at all. Why can't you understand that ?