Kerry is known for her charitable and human rights endeavours, as well as her positive onscreen characters, but she quickly signed on to director Ryan Murphy's project, also starring Meryl Streep, Nicole Kidman, and James Corden, because she wanted to switch things up and play the "bad guy".
"('The Prom') is about these two girls who want to go to prom together because they're in love, and the head of the PTA (Parent-Teacher Association) cancels the prom because she does not believe two girls should be allowed to go together," she tells America's "Live with Kelly and Ryan".
"And I play the president of the PTA so I'm basically the bad guy in this movie. I'm the villain who will not accept love is love."
Kerry's character is mum to one of the lesbian schoolgirls, and though the activist would have no problem accepting her own child's sexuality, she had to approach the role with real "compassion".
"I do have a really progressive ideology," she continues. "I'm very inclusive and believe in human rights across the board, and freedom around who you should love and who you are. But it was really a good exercise for me to not have judgement with this mum who is struggling with her daughter's identity, and to try to put myself into her shoes."
"She does love her child and she's trying to do what is best for her child, so what is she afraid of? What is she struggling with? So (I had to) try and come at it with more compassion and understanding."
And she thinks "The Prom" has plenty of important lessons for its audience, especially in America as the country remains divided following the election of President-elect Joe Biden last month (Nov20) to replace incumbent leader Donald Trump when he leaves the White House in January (21).
"We have to try to understand each other," Washington adds. "That's how we're going to heal this country - if we really do a better job of trying to understand each other."