The boy who brought the wagon to Kane was disbelieiving and heartbroken when Kane
threw his tin star into the dirt. Kane had most likely been a hero to the kid. Maybe Kane saved him from a similar fate of risking his life for people who, "Just don't care." That was a powerful message for naive starstruck youth.
Strangely enough, that bit was a rewrite of the original version where the towns people who refused to help out the marshall, all come out to congratulate him and Cooper angrily yells "Burn in hell, you incontinent pack of gutless pussies!" Apparently the studio thought while more realistic in terms of emotion, it would not be received well by audiences of the 1950's.
"There's a little good inside everyone. Sometimes it just takes a scalpel to find it." - Me