The US was also fine with Iraq doing it. When Iraq gassed a Kurdish village in 1988, the US actually blocked condemnation of Iraq in the UN Security Council an

The US was also fine with Iraq doing it. When Iraq gassed a Kurdish village in 1988, the US actually blocked condemnation of Iraq in the UN Security Council and tried to redirect blame towards Iran. The US only started making a big deal of Iraq's attacks on the Kurds years later, when Iraq had gone from being an ally to an enemy.