Anyone in any sect can become a Christian if he or she puts their faith and trust in Jesus Christ and Him alone. They may not be able to stay in their sect after doing that, but anyone can come to know Christ in a personal way and have a loving and personal relationship with Him as our Abba Father, or Daddy. I KNOW whom I have believed and I WILL be with Him for all eternity. That's called eternal assurance (or INsurance).
So, the theology doesn't matter! I guess that makes Arians, Nestorians, Monophysites, Moromons and Jeohva's Witnesses, Bogomils and Ebionites all part of one happy "church' and family. They all, one way or another, call on Christ.
Doesn't the NT say that the devils believe and tremble as well? What does that make them?