I don't know how you read it, but that verse says pretty definitively that churches/people who threaten others with Hell are the ones who deserve to go to Hell.
I see it as Joe Smith really hating Catholics.
(Program of The Church of Jesus Christ of Latter-day Saints, p. 226)
Mormons don't believe in a fire-and-brimstone Hell, they believe that a person's pain for his or her own self via their conscience, or their greed for something greater(i.e. the Celestial kingdom) is sufficient punishment.
If that is the case, then it would only be another case of people not believing in what their own book says.
How about these?
Moroni 8:14 Behold I say unto you, that he that supposeth that little children need baptism is in the gall of bitterness and in the bonds of iniquity, for he hath neither faith, hope, nor charity; wherefore, should he be cut off while in the thought, he must go down to hell.
8:21 Wo unto such, for they are in danger of
death, hell, and an endless torment. I speak it boldly; God hath commanded me. Listen unto them and give heed, or they stand against you at the judgment-seat of Christ.
Emphasis added. The "that which shal come to pass" and "wo"s where already there, for some reason. Joe Smith really hated Catholics.
It's insane? So because it's different, it's obviously insane right?
It is insane because it is a groundless thought that sounds exactly like the rantings of a madman. In case you haven't realized by this, I think all religions are insane, and they are hardly "different" or rare.
He can believe whatever he wants, whether he has proof for it or not.
But doing so is insane.
Hes not trying to convince you, and he doesn't affect you at all. Again, HE does not affect YOU at all with his belife
Really? Lets say that there is not only one guy, but millions. These millions of guys form groups that become very influential. Of course they don't want other people's minds to succumb to alien influence, so they start spreading the word. Then a president comes into power, promising "To free us from the alien oppression". Our money eventually gets "YOU CAN'T HAVE OUR BRAIN, ALIENS!" written on it to fight them off. Is it effecting me yet?
So he should definitly be allowed to like it and believe it
Allowed to, sure, but should he believe it?
He doesn't have a mental problem, so you shouldn't be worried.
How can you tell if it is a mental problem?
Oh, one important caveat: Mormons believe that sons of perdition and murderers go to Outer Darkness. A son of perdition is considered the utmost sinner...it means that they do believe in God, they know the truth, but they still choose evil. The Outer Darkness is like Purgatory, not Hell, but souls who get thrown in there can never get out or be forgiven.
I am starting to think you are making this up. My BOM has nothing about this in it.