Hell, we're certain that Trump couldn't give a crap about having flawless grammar and it should be noted that De Niro did take the first verbal shot in their recent war of words, but if you're ever going to have a pop at someone's intelligence, make sure that you get it right on your own end.
The crowd at New York's Radio City Music Hall cheered his remarks, though he was later criticized for stooping to Trump's name-calling level. He delivered his response on his Twitter account while on his way back to the United States.
De Niro has also made recent TV appearances on Saturday Night Live as none other than Robert Mueller, the special counsel overseeing the Russian Federation probe the President has repeatedly decried as a "witch hunt".
In the catalog of nicknames Trump has bestowed upon his detractors, "Punchy" has to be his worst yet. "It's no longer 'Down with Trump.' It's f- Trump". I watched him last night and truly believe he may be 'punch-drunk'.
Manchester United new boy Diogo Dalot can already speak like a Mancunian
The midfielder's existing deal is set to expire on June 30 and if new terms are not agreed he will be able to leave on a free transfer.
He famously said he wanted to punch Trump "in the face" during the 2016 US Election, called him a "f***ing fool" and the "baby-in-chief" in January 2018, and the following month said the US was now suffering from a "case of temporary insanity".
Find Trump's tweet and De Niro's latest comments below. (Pictured at the 2005 Tribeca Film Festival).
And, after the f-bombs at the Tonys on Sunday night, it looks like De Niro is staying true to his word about speaking out.
De Niro has attacked President Trump on previous occasions, describing him in 2016 as "blatantly stupid", "totally nuts" and an "idiot".
He said in Toronto: "I just want to make a note of apology for the idiotic behaviour of my president". "It's a disgrace. And I apologize to [Canadian Prime Minister] Justin Trudeau and the other people at the G7".