One by one, celebrities who have expressed frustration with Donald Trump’s birther campaign have become targets of the “Celebrity Apprentice” host’s acid tongue. Whoopi Goldberg and Jerry Seinfeld, among others, have found themselves on the bad side of the would-be presidential candidate in recent weeks.

Now we can add two-time Oscar winner Robert De Niro to the list, according to The Hollywood Reporter.

Apparently what went down is this: Without naming Trump, De Niro implied during an interview Saturday at the Tribeca Film Festival that the birther issue is unsupported by facts. "I won’t mention names, but certain people in the news the last couple weeks, just, what are they doing?" he said. "It’s crazy. They’re making statements about people that they don’t even back up. Go get the facts before you start saying things about people."

That was enough to earn an angry reply from Trump, who lashed out today at De Niro on “Fox & Friends.” Among the highlights: “I like his acting, but in terms of when I watch him doing interviews and various other things, we’re not dealing with Albert Einstein.” And: “He’s not the brightest bulb on the planet.”

De Niro won Oscars for “The Godfather: Part II” in 1975 and “Raging Bull” in 1981.