There is an opinion based on the Midrash, that during the time that the spies were scouting the land, a major funeral was taking place. The claim was that there was major mourning for the saintly gentile known as איוב or Job.
Hashem's intention was to protect the spies by having the masses being preoccupied with the loss of a great leader. This way, they would not be discovered spying out the land.
They took this act of protection by Hashem in the wrong way. They spoke badly and said that it was a land that devours its inhabitants and everywhere they went, there were funerals.
The lesson here is that often we experience similar frustrations. Our good intentions are misread and are looked at in a derogatory manner. We are accused of having selfish motives when we sincerely wished to do an altruistic act.
The ארחות צדיקים reassures us by saying that even when our good intentions are seen in a negative light, Hashem knows. This knowledge should actually bring us joy because the truth wins in the end.