"Joseph Smith receiving the gold Nephi plates (the book of Mormon) from the angel Moroni." (so the story goes)
"I am amazed that you are so quickly deserting Him who called you by the grace of Christ, for a different gospel; which is really not another; only there are some who are disturbing you, and want to distort the gospel of Christ. But even though we, or an angel from heaven, should preach to you a gospel contrary to that which we have preached to you, let him be accursed." Gal 1:6-8.
"Let no one keep defrauding you of your prize by delighting in self-abasement and the worship of the angels, taking his stand on visions he has seen, inflated without cause by his fleshly mind" Col 2:18.
Even if the so called angel, "Moroni", really did appear to Joseph Smith, he is still accursed because the gospel of the Book of Mormon is very different from the gospel of the Bible. Since the Book of Mormon does not conform to the standard of the Bible, it is not Christian, but condemned being a new and false gospel.