Matt Fradd famously called the Book of Mormon demonic and made a video on 7 reasons Joseph Smith is a false prophet, Trent Horn debated the Book of Mormon and even did a video with a Latter-day Saint on whether the Church is demonic, Joe Heschmeyer has done multiple videos on the Church plus debates and a multi-hour interview with Fradd.
Yet NONE of Ethan's fellow Catholics treat this argument as a silver bullet like Ethan does, in fact I'm not sure they even mention it, maybe in passing. Why?
Because Ethan's argument only carried weight if you use his assumptions. Treasure guardians have to be demons. It's impossible that Joseph mistook a spirit for a treasure guardian (remember the disciples reaction to Jesus walking on water?). It's impossible that Joseph's understandings of spirits when he was 17 was underdeveloped. It's impossible that the Smith families views on spirits don't fit neatly into Ethan's categories. And why is Ethan taking this as gospel truth when he said in the debate that Joseph was totally untrustworthy?
Here are the descriptions of the angel in the earliest accounts :
1829 - Josephs uncle "he writes that the angel of the Lord has revealed to him the hidden treasures of wisdom & knowledge, even divine revelation, which has lain in the bowels of the earth for thousands of years [and] is at last made known to him, he says he has eyes to see things that art not, and then has the audacity to say they are; and the angel of the Lord (Devil it should be) has put me in possession of great wealth,"
1829 - Palmyra newspaper: "Joseph Smith, of Manchester, Ontario county, reported that he had been visited in a dream by the spirit of the Almighty and informed that in a certain hill in that town, was deposited this Golden Bible, containing an ancient record of a divine nature and origin"
1830 - Three witnesses: shown plates by angel of the Lord (though this isn't directly and account of Moroni's visit)
1830 - D&C 20 (Joseph's actual first account of the event) "For after that <it> truly was manifested unto this first Elder that he had Received a remission of his sins he was entangeled again in the vanities of the world but after truly Repenting God ministered unto him by an Holy Angel whose countenance was as Lightning & whose garments were pure & white above all whiteness & gave unto him Commandments which inspired him from on high & gave unto him power by the means of which was before prepared that he should translate a Book which Book contained a record of a fallen People & also the fulness of the Gospel of Jesus Christ"
1830 - Letter from non-LDs source "He [Smith] claimed that the angel of the Lord had appeared and made known to him that in the neighborhood of Palmyra, there were golden plates hidden in the earth on which was written the fate of a Jewish prophet’s family, together with many as yet unfulfilled prophesies, and that the Lord had appointed him to translate the same from ancient languages into English."
1832 - unpublished Joseph Smith history - "when I was seventeen years of age I called again upon the Lord and he shewed unto me a heavenly vision for behold an angel of the Lord came and stood before me and it was by night and he called me by name and he said the Lord had forgiven me my sins and he revealed unto me that in the Town of Manchester Ontario County N.Y. there was plates of gold upon which there was engravings which was engraven by Maroni & his fathers the servants of the living God in ancient days."
Joseph reports going to the hill and being unable to obtain the plates because he wanted to use them for personal gain.
1834 - Mormonism Unvailed accounts of spirits with heavier treasure guardian and occult themes (like Moroni being a toad at first)
Hopefully you can see why even Christians, including most Catholics, don't use accounts about Moroni as definitive proof of demons. Usually they will say Joseph was influenced by treasure guardian beliefs and there is a possibility of demonic influence, but its not conclusive.
Other stories Ethan used and other conclusions he came to follow a similar pattern. I almost have to respect the self-confidence required to be so confident in such a fringe viewpoint.