How did the u. s justify using agent orange and napalm during war?

They justified it by wanting to win a protracted, unpopular war.

Napalm & Agent Orange. Napalm was first used in flamethrowers for U.S. ground troops; they burned down sections of forest and bushes in hopes of eliminating any enemy guerrilla fighters. The Vietnam Red Cross recorded over 4.8 million deaths and 400,000 children born with birth defects due to exposure to Agent Orange.

d.he wanted to send diplomats to communist countries.

this is a good question! i'll do some research and come back when i have the answer!