The word that best describes the tone expressed in this passage is "frustration".
From the passage, we see that the speaker is likely speaking out of frustration. It's likely that the boys in question were arrested and so out of the frustration of their arrest, the speaker speaks in order to defend the boys. Thereby, the speaker speaks to clarify the issue.
The City Mouse and the Country Mouse A City Mouse and a Country Mouse were acquaintances (friends), and the Country Mouse one day invited his friend to come and see him at his home in the fields. The City Mouse came, and they sat down to a dinner of roots.