Editor's note: Watch more of Anderson Cooper's exclusive interview with Yoko Ono Wednesday night on AC360° beginning at 10 pm ET.
(CNN) -- John Lennon would have turned 70 years old this month, and were the late Beatle alive today, he might be sitting in a rocking chair in Cornwall, England, with wife Yoko Ono waiting for a postcard from their son, Sean, Ono said in an exclusive interview with CNN's Anderson Cooper.
But eventually his spirit for activism would have roused him out of his retirement rocker, Ono added.
"I'm sure that, if he got to be 70, then he would have forgotten all of that: No, we have to do something now. And I'm sure this is when he would have been totally activist," Ono said. The wide-ranging three-part interview continues with the second installment on Cooper's "AC360" Wednesday night.
In the interview, Ono spoke about being unfairly blamed for the breakup of the Beatles and how she can't forgive Mark David Chapman, the maniacal fan who fatally shot Lennon in 1980.
She also strolled with Cooper through Central Park's Strawberry Fields, dedicated to Lennon and named after the song "Strawberry Fields Forever," written by Lennon and fellow Beatle Paul McCartney.
Lovers of Lennon's music should celebrate his 70th birthday anniversary, which occurred October 9, by remembering his expansive spirit, Ono said.
"I know that people loved him for what he has given them because he did give a lot. And all his beautiful ideas, they're not like seeds in their hearts that grow: We all have this huge, huge forest of ideas that we share," she said.
"I would say that let's not think about the fact that he passed away, but let's think about, you know, we should celebrate that he was here. The fact that he was here really helped the world.
"So I want people to remember that and not when he passed away. But of course he did pass away, and I don't know, but by saying that I think -- concentrating on his birthday -- I think somehow I changed the kind of configuration of things," Ono said.
Ono continues to live in the Manhattan apartment building, the Dakota, where the couple and their son, Sean, lived. It was outside that building where Chapman gunned down Lennon after Lennon had earlier given him an autograph.
Ono marked Lennon's birthday by visiting her memorial to him: the Imagine Peace Tower in Iceland, a tower made of light, which she visits every year. She selected the Atlantic island country "because Iceland is the top north in the map. And north is wisdom and power, and the wisdom and power from the north would just go spread all over the world," she said.
Now 77, Ono has been remastering Lennon's music, and she performed with her Plastic Ono Band during Iceland's memorial celebration.
She recalled how she first learned of Lennon's death -- in the hospital where he was taken for his bullet wounds. It's a time she doesn't care to ponder.
"When I went to the hospital and I was waiting and the doctor came and he was carrying something of John's, like, his ring, and that's when I thought, ah, what is it, what is it? Just funny feeling about it, and when he said that he passed away, I said no, he didn't, he's alive, You know, very, very upset about it. I just refused to think that he died."
Whenever Lennon's murderer is up for parole, Ono speaks out against his release.
"I'm very concerned about that because, you know, he's not a very stable person," she said. She's skeptical of any portrayal of Chapman as a "very, very agreeable" person.
"So now that he's very charming or something, well, he was perfectly charming then too. So I don't really have a trust for him -- for what would happen when he comes out," she said.
Chapman killed Lennon on December 8, 1980. At the time, Lennon was 40; Chapman, 25.
"Well he got the autograph from John that very day," Ono said. "You know, we were going to go to the studio, and John was a very, very astute person in that sense. To go to studio right (on) time. Not an hour later or two hours later. Most musicians didn't really care, but he was very prompt about those things. So we had the car, I got in the car, and I saw that John was still signing autographs.
"I said, 'John, we have to go now,' and he said, 'Yeah, OK, Yoko,' " she added.
Forgiveness for the murder remains a difficult matter, she said.
"Well, I don't really know, I have to think about that," Ono said. "But Sean especially and me too (are) still living a very strong situation. It didn't suddenly go away. ... So it's a very difficult situation and we can't get out of it."
Part of Beatles lore is that Strawberry Fields was actually an orphanage near Lennon's childhood home, and whenever Lennon acted like a bad boy, his mother and aunt threatened to send him there, Ono said.
"He was having a love-hate relationship with Strawberry Field. It was a very big thing in his life," Ono said. "So then he made a song out of it. See, by having a very painful memory and changing that into a song, and then that was changed to here, into a park."
Over the years, Ono has been characterized by some as the overbearing wife who caused the breakup of one of the most famous bands of the 20th century. Born in Japan, she blames racism as well as sexism for the unfounded charge, she said. The Beatles had long been having internal problems, she said.
"I think I was used as a scapegoat, and it's a very easy scapegoat, a Japanese woman and whatever," Ono said. "Sexism, racism, but also just remember that the United States and Britain were fighting with Japan in World War II."
While she was stung by such characterizations, she and Lennon went on to enjoy a full marriage.
Asked if the finger-pointing hurt her, Ono responded, "Well, it did in a way. But you know, it was sort of like a distant thing in a way, because John and I were so close. And we were just totally involved in each other and in our work.
"You know," she added, "I just kept on being -- getting ideas. And he was, too. So that was much more exciting."
Watch Anderson Cooper 360° weeknights 8pm ET. For the latest from AC360° click here.