The two men were among Hollywood's elite when they were accused of sexual misconduct in 2017.
Both have been ostracised by the film industry while awaiting trial and Spacey's performance in Sir Ridley Scott's 2017 drama All The Money In The World was removed after the film was finished, costing millions of pounds in reshoots.
Dame Judi, 84, told the Radio Times: "What kind of agony is that?
"Are we going to negate ten years at the Old Vic and everything that he (Spacey) did (as artistic director) - how wonderful he's been in all those films?
"Are we just not going to see all those films that Harvey produced? You cannot deny somebody a talent.
"You might as well never look at a Caravaggio painting (he was a murderer). You might as well never have gone to see Noel Coward (accused of predatory behaviour)."
Dame Judi did not defend the behaviour of Spacey or Weinstein and has publicly condemned both men.
She was a friend of two-time Oscar-winner Spacey, who comforted her following the death of her husband Michael Williams in 2001, while Dame Judi credits film producer Weinstein with her Hollywood breakthrough.
Weinstein's downfall precipitated the rise of the #MeToo movement when dozens of women came forward in October 2017 to claim he had assaulted them.
The once all-powerful movie mogul was booted out of the Academy and his film studio went bankrupt. He is awaiting trial for rape in New York.
Spacey was accused of inappropriate behaviour by actor Anthony Rapp, who alleged he was 14 when a 26-year-old Spacey came on to him at a party.
American Beauty star Spacey said he did not remember the incident but apologised. He has since faced more allegations of sexual assault and is awaiting trial in the US.
The full interview is in this week's Radio Times.