Whats Camus' reason for making the Arab a murderer?

Camus makes the Arab a murderer to influence the reader's
response to the dilemma Daru faces in the story, based upon Camus' political concerns at
that time between Algiers and France.

The reader expects
Daru to find the Arab repugnant so that when Daru is "ordered" to take him to jail, we
expect that Daru would follow directions without a second thought.  First, because the
Arab has committed a terrible crime (murder), rather than just assault or thievery.
 Second, Camus makes the prisoner an Arab because at the time he wrote the story, the
Arab's predicament would not have elicited much sympathy, as Arabs were not generally
accepted or respected, so if Daru was mean to him, few would have cared, but might even
expect it.  Camus makes a strong personal statement in treating the Arab like a "guest"
in light of this.

Centrally, Daru's refusal to take up any
kind of gun against the Arab shows Daru's refusal to take sides in the conflict between
the French and Arabs.  This is Camus speaking to his personal refusal to choose sides in
the problems between the Algerians and the
French.

Ironically, Daru cares more for the Arab than the
Arab's own people: Daru cares for him in his home, and offers him the chance to escape,
even though the Arab does not take the opportunity.  All the Arab's friends do is
threaten Daru, blaming him, instead, for the Arab's
incarceration.