After Lamoni was converted to the truth, he did not participate in the feast / holiday of his father. Lamoni told his father why, and was surprised that his father did not agree with him but was actually angry with him. Lamoni father not only told him to separate himself who taught him these truths, but to kill him, and went off on a rant how what Ammon taught was a lie. This is very typical of what happens when someone converts to the truth and lets go of the pagan holidays.

Alma (LDS 20:9-14) (RLDS 12:191-98)
9 And behold, the father of Lamoni said unto him: WHY DID YE NOT COME TO THE FEAST on that great day when I made a feast unto my sons, and unto my people? 10 And he also said: Whither art thou going with this Nephite, who is one of the children of a liar? 11 And it came to pass that Lamoni rehearsed unto him whither he was going, for he feared to offend him. 12 And he also TOLD HIM ALL THE CAUSE OF HIS TARRYING IN HIS OWN KINGDOM, that he DID NOT GO unto his father TO THE FEAST which he had prepared. 13 And now when Lamoni had rehearsed unto him all these things, behold, to his ASTONISHMENT, his FATHER was ANGRY with him, and said: Lamoni, thou art going to deliver these Nephites, who are sons of a LIAR. Behold, he robbed our fathers; and now his children are also come amongst us that they may, by their cunning and their LYINGS, DECEIVE us, that they again may ROB us of our property. 14 Now the father of Lamoni commanded him that he should SLAY Ammon with the sword. And he also commanded him that he should not go to the land of Middoni, but that he should return with him to the land of Ishmael.