Why might some people have supported king's speaking out against the war? why might have others opposed it?

Because like king, some people believed that the war only brought negative things for the country, such as poverty , death, and economic instability.
Meanwhile, some people believe that they're doing the war for the right cause (i.e : destroying communism and other cruelties) , so they chose to oppose king

Ithink that would be false, hope that this .