Why did the U.S. give Saddam Hussein chemical warfare weapons?

He used these on his own people (mostly the Kurds), and on the Iranians during the Iran-Iraq war. The Iraqi people have suffered not only from these weapons, but also the continuous funding sent from the U.S. He also imposed Sharia Law, which as we all know can be very harsh and brutal. Why did the U.S. support such a murderous regime and then turn their backs on Saddam during operation desert storm? And why don't most people feel bad for the Iraqis? My grandpa is Iraqi, and he cried telling me about the horrors of Saddam's Regime.