It shows the doer of the action.It comes before verb and indicates this action or work is done by it/him/her etc.Ex.Susan switched off the lights. Who switched off the lights? The answer is Susan (subject of the sentence)
These individuals are fighting because they have conflicting ideas. One side believes that white people are superior to every other race, while the other believes all races are equal, and not one is better than the other.
It is because of this strong disagreement that these people are at each other's throats. Add in an immense passion for your beliefs, and that can spark violence.
Hopefully, this helps! =)