Messing, who has been outspoken about her anti-Trump politics in recent years, ripped the president for what many critics have called the "photo op" that he held in front of St. John's Cathedral, which suffered from a fire late Sunday amid the George Floyd protests.
Following his address in the Rose Garden, Trump walked from the White House to the historic church across Lafayette Park and held up a Bible while standing alongside top administration officials and aides.
However, the "Will & Grace" star suspected that it was a "dog whistle" to racists and bigots.
"A dog whistle to white nationalists and Nazis," Messing wrote while sharing an image of Trump holding a Bible next to an image of Hitler, who also appears to be holding a Bible. The image was captioned with "This is no accident!"
However, Messing was slammed by critics, many of them pointing out pointed out that the image of Hitler was actually edited from the original photograph, which showed the dictator raising his hand without holding any book.
"Hollywood elites: anyone holding a Bible is Hitler! This is idiocy," said Sen. Ted Cruz, R-Texas.
"Except when the Hitler photo is FAKE it ends up being a dog whistle for desperate, hateful people with no moral compass, like you. Every time you do things like this you lose more and more support. Just. Stop," radio host Larry O'Conner scolded the actress.
"Please check stuff before you spread it. The Hitler photo is fake," BuzzFeed News media editor Craig Silverman told Messing
Messing later thanked Silverman for pointing out the false image she shared, but still stood by the comparison.
"Thank you Craig for informing me, I hadn’t known it was photoshopped. I still stand, however, by the comparison of Trump to an authoritarian dictator," Messing wrote. "He did threaten to turn our military against our citizens. He used police might, horses,& teargas on peaceful protesters. Citizens protesting systemic violence against black ppl by police. Trump wants them 'Dominated.' That says it all."