Why doesn't the swallow like little boys?

The swallow, reluctant to concede to the Happy Prince's request, tells him that he is not sure that he likes little boys in general. He bases this assumption on a particular incident, which he relates to the Prince. The previous summer, the swallow had encountered the miller's boys who had thrown stones at him. Although they had never succeeded in actually hitting him, because the swallow was far too agile for that, they had frightened him and made him distrust young boys as a general rule.
In the end, however, the Happy Prince does not seem moved by this story. On the contrary, he "looked so sad," so the swallow decided he would stay with him anyway and then agrees to be the Prince's messenger the following day and take the ruby, as requested, from the hilt of the Prince's sword to the house of the little boy and his mother.