Question

the origins of segregation
legislation is powerless to eliminate racial instincts or to abolish distinctions based upon physical differences.... if the civil and political rights of both races be equal, one cannot be inferior to the other civilly or politically. if one race be inferior to the other socially, the constitution of the united states cannot put them upon the same plane.
what is the main purpose of this passage?
to criticize louisiana for its segregation of railroad cars
to argue against those who oppose segregation
to defend segregation as an acceptable practice
to deny that legal segregation is necessary

Explanation:

The text argues legislation can't eliminate racial instincts and if civil - political rights are equal, social inferiority can't be forced by the Constitution, implying legal segregation isn't needed.

Answer:

To deny that legal segregation is necessary