Except that it is classified as a war crime under Article 54 of Protocol I of the Geneva Convention:
It is prohibited to attack, destroy, remove or render useless objects indispensable to the survival of the civilian population, such as foodstuffs, agricultural areas for the production of foodstuffs, crops, livestock, drinking water installations and supplies and irrigation works, for the specific purpose of denying them for their sustenance value to the civilian population or to the adverse Party, whatever the motive, whether in order to starve out civilians, to cause them to
move away, or for any other motive.
From what I purpose of Agent Orange was to deny the Viet Cong supplies in South Vietnam. "Friendly" South Vietnamese were to be relocated to strategic hamlets and provided food if needed.
This was not an attempt to starve the civilian population.
You are being down voted but yours is the only correct attitude when it comes to war. There are no rules, justice, good guys, bad guys, innocents or the guilty. These are luxuries we afford ourselves when talking about war diatanced from us by a certain measure of time. The only truth that exists when war is ongoing is the human capacity for evil expressed through some supposed agenda and dead bodies.
It is prohibited to attack, destroy, remove or render useless objects indispensable to the survival of the civilian population, such as foodstuffs, agricultural areas for the production of foodstuffs, crops, livestock, drinking water installations and supplies and irrigation works, for the specific purpose of denying them for their sustenance value to the civilian population or to the adverse Party, whatever the motive, whether in order to starve out civilians, to cause them to move away, or for any other motive.