Who can tell how long their feelings had been rankling in their bosoms; how long, or how much they had borne; a single drop will make the cup run over, when filled up to the brim; a single spark will ignite the mine, that, by its explosion, will scatter destruction around it; and may not one foolish indiscretion, one thoughtless act of contumely or wrong, arouse to vengeance the passions that have long been burning, though concealed?
With the same dispositions and tempers as ourselves, they are subject to the same impulses and infirmities.

Little accustomed to restrain their feelings, it is natural, that when goaded beyond endurance, the effect should be violent, and fatal to those who roused them;--the smothered fire but bursts out the stronger from having been pent up; and the rankling passions are but fanned into wilder fury, from having been repressed.
Seventhly, There are also other considerations to be taken into the account, when we form our opinion of the character and conduct of the natives, to which we do not frequently allow their due weight and importance, but which will fully account for aggressions having been committed by natives upon unoffending individuals, and even sometimes upon those who have treated them kindly.

First, that the native considers it a virtue to revenge an injury.

Secondly, if he cannot revenge it upon the actual individual who injured him, he thinks that the offence is equally expiated if he can do so upon any other of the same race; he does not look upon it as the offence of an individual, but as an act of war on the part of the nation, and he takes the first opportunity of making a reprisal upon any one of the enemy who may happen to fall in his way; no matter whether that person injured him or not, or whether he knew of the offence having been committed, or the war declared.

And is not the custom of civilized powers very similar to this?
Admitting that civilization, and refinement, have modified the horrors of such a system, the principle is still the same.