Why does Gene feel that it is important to avoid making fun of Leper Lepellier?

Gene feels its important to avoid making fun of Leper (and very difficult) because of his youthful exhuberance. The rest of the boys are digging out train tracks and Leper is off on his skis searching for a beaver dam. He's timid and innocent.... and mentally too young for the changes that are coming. Gene is right.