Alma 30:16 - 30:20
Alma 30:16 Ye look forward and say that ye see a remission of your sins. But behold, it is the effect of a frenzied mind; and this derangement of your minds comes because of the traditions of your fathers, which lead you away into a belief of things which are not so.
Korihor renounces the concept of a remission of sins. The feeling that comes from the relief of being forgiven of sins is the effects of a deranged mind. There is no such thing according to Korihor. Again this doctrine is nothing more than the traditions passed down.
Alma 30:17 And many more such things did he say unto them, telling them that there could be no atonement made for the sins of men, but every man fared in this life according to the management of the creature; therefore every man prospered according to his genius, and that every man conquered according to his strength; and whatsoever a man did was no crime.
There were many more doctrines that Korihor preached against, particularly the atonement. He said that what a man achieved in this life was the result of his talents and abilities. If a man was smarter than another, he did better. And regardless, whatever means he used to get ahead was no crime.
I am going to assume that these would be actions that were not considered criminal. However, a person could do anything short of that even if considered immoral or not being very nice to the weak and not so smart.
Alma 30:18 And thus he did preach unto them, leading away the hearts of many, causing them to lift up their heads in their wickedness, yea, leading away many women, and also men, to commit whoredoms—telling them that when a man was dead, that was the end thereof.
A lot of people liked what Korihor was preaching and he had gathered many followers to his precepts. Many were not acting like Korihor and were committing all kinds of wickedness. Many women were going along with him life style and became very wicked in their behavior. Since he was telling the people that when you died that was all there was so why not have fun until then.
Alma 30:19 Now this man went over to the land of Jershon also, to preach these things among the people of Ammon, who were once the people of the Lamanites.
Korihor then went over to the land of Jershon where the Ammonites were living.
Alma 30:20 But behold they were more wise than many of the Nephites; for they took him, and bound him, and carried him before Ammon, who was a high priest over that people.
However, he was not received at all by these Lamanite converts. In fact, they handcuff him to took him before Ammon, who was the high priest over the Ammonites.