On Mr Biden challenging him to a fight, Mr Trump said, "He'd be down, faster than Greg would take him down".
Needless to say, Trump's praise of Gianforte - who plead guilty to misdemeanor assault, only adds to the grim view of an America where "free speech" is only protected if it uplifts the current administration.
Gianforte pleaded guilty to misdemeanor assault a year ago after he laid hands on Ben Jacobs, a reporter for The Guardian, and was sentenced to 40 hours of community service, 20 hours of anger-management counseling and payment of a $385 fine.
But as he left Washington to travel to the rally on Thursday, Mr Trump warned of "very severe" consequences for the apparent killing.
"I shouldn't say this", he said, then adding "there's nothing to be embarrassed about".
He recalled hearing the story when he was overseas and admitted that at first, he anxious that Gianforte might lose the election. The judge called Gianforte's actions "totally unacceptable" but gave him a six-month deferred sentence. "I know Montana pretty well, I think it might help him.' And it did". He detailed that he saw a Trump supporter doing wrestling moves in the crowd while Trump continued his attack on reporters.
Trump commented at the rally that upon hearing of the assault, he thought it might hurt Gianforte's chances.
Mr Gianforte, who attended the rally with the President, is up for re-election in November and faces former state legislator Kathleen Williams.
Trump's comments come as events are unfolding in the disappearance of Saudi journalist Jamal Khashoggi, who was last seen entering the Saudi consulate in Turkey on October 2. Saudi officials have denied his disappearance was a result of foul-play on their part. Trump said on Thursday that it "certainly looks" as though Khashoggi is dead. "We hope decent people will denounce these comments and that the president will see fit to apologize for them".