Alma 30:11 - 30:15
Alma 30:11 For there was a law that men should be judged according to their crimes. Nevertheless, there was no law against a man’s belief; therefore, a man was punished only for the crimes which he had done; therefore all men were on equal grounds.
The Nephites had laws in place to punished criminals for criminal acts, but there was no laws prohibiting a person from hold a particular belief. Everyone was treated the same when it came to crimes against society.
Alma 30:12 And this Anti-Christ, whose name was Korihor, (and the law could have no hold upon him) began to preach unto the people that there should be no Christ. And after this manner did he preach, saying:
The man who now came into Zarahemla to preach his doctrine was an anti-Christ. He was called that because he preached that there was no such thing as a "Christ."
Alma 30:13 O ye that are bound down under a foolish and a vain hope, why do ye yoke yourselves with such foolish things? Why do ye look for a Christ? For no man can know of anything which is to come.
His rhetoric centered on the argument that no one could know of things to come. Therefore anyone who is looking towards the coming of the Messiah is delusional and has adopted a belief that will not allow themselves to be all they can be. The hope that some mythical person will save them from some bad fate is only foolishness.
Alma 30:14 Behold, these things which ye call prophecies, which ye say are handed down by holy prophets, behold, they are foolish traditions of your fathers.
The prophecies given to the people over time are nothing but traditions. There is no basis in fact for any of the words spoken by them was this anti_Christ's words.
Alma 30:15 How do ye know of their surety? Behold, ye cannot know of things which ye do not see; therefore ye cannot know that there shall be a Christ.
This anti-Christ continued with the argument that because you cannot see it means you cannot prove it or know of its existance. There is no way, according to this anti-Christ, that one can know if a Christ will come at some point in the future.