Soleimani, the head of the Islamic Revolutionary Guard Corps' elite Quds Force, was described by Secretary of State Mike Pompeo as being just as dangerous as ISIS leader Abu Bakr al-Baghdadi, who killed himself during a raid by U.S.-led forces in Syria this past October.
The "Fahrenheit 9/11" director, however, responded to the strike by addressing "fellow Americans."
"Hello fellow Americans. Do you know this man? Did you know he was your enemy? What? Never heard of him?" Moore tweeted. "By the end of today you will be trained to hate him. You will be glad Trump had him assassinated. You will do as you are told. Get ready to send your sons & daughters off 2 war."
Moore was criticized for the tweet on social media for being so dismissive of the Soleimani killing.
"You are so stupid. This man was a famous Terrorist and killed thousands of people - women and children," Yahoo News journalist Tobias Huch reacted.
"A lot of people didn’t know about Osama Bin Laden until 9/11 either Mike," New York Post reporter Jon Levine wrote.
Moore isn't the only celebrity to be outspoken on the airstrike. Actress Rose McGowan sent out her own series of tweets early Friday, attacking the United States and leaving some followers questioning her sanity.
"Dear #Iran, The USA has disrespected your country, your flag, your people. 52% of us humbly apologize. We want peace with your nation. We are being held hostage by a terrorist regime. We do not know how to escape. Please do not kill us. #Soleimani," she wrote.
Fox News' Frank Miles and Melissa Roberto contributed to this report.