(CNN) -- A Northwestern University professor who allowed a couple to demonstrate a sex toy in front of students apologized Saturday, saying he regrets upsetting people and should not have allowed it.

While psychology Professor J. Michael Bailey called the incident a "mistake," he also said the February 21 incident provoked important debate about issues including academic freedom and the effect of sexual attitudes on education.

"I am sorry that these issues that are important have been raised in this way, instead of directly through words and arguments in the classroom," Bailey told CNN on Saturday. "That said, now that they have been raised, let's talk."

It was the first time Bailey has expressed regret for the incident, which drew national headlines. University President Morton Schapiro had said he was "troubled and disappointed" by it and had ordered an investigation.

The event took place in an optional after-class session for Bailey's human sexuality course at the prestigious private university near Chicago. Bailey previously explained he wanted students to learn about sexual diversity and information from "real people."

Students who witnessed the incident had been told repeatedly by a guest speaker that what was about to happen would be graphic, the professor said. About 100 students chose to attend following a larger lecture, affiliate WGN said.

Bailey invited speaker Ken Melvoin-Berg, co-owner of Weird Chicago Tours, who brought a woman and a man for a discussion on the female orgasm. Melvoin-Berg suggested they demonstrate use of high-powered equipment they brought, said the professor, who agreed to the idea.

Melvoin-Berg told CNN affiliate WLS that they received "100% positive feedback during and after" the demonstration, but some students left while it was happening.

"For me, I'm glad I didn't see it. It was a little too explicit for me, and if I were in the class, if I would have stayed for the demonstration, I probably would have left. I know a couple of my friends did get up and leave," student Diana Lorenzini told CNN affiliate WLS.

Brianne Williams, another student, said "Doctor Michael Bailey is one of our finest professors here, and his class is about opening people's minds up."

Bailey said he was surprised the incident generated so much controversy.

"During a time of financial crisis, war and global warming, this story has been a top news story for more than two days," he said in a statement posted on the WLS website. "That this is so reveals a stark difference of opinion between people like me, who see absolutely no moral harm in what happened, and those who believe it was profoundly wrong."

Bailey told CNN he is receiving a "tremendous amount of support" from colleagues, students, parents of students, alumni and academics from all over the world.

As a researcher of human sexuality and sexual orientation, Bailey said he has encountered controversy over his work before and has even been attacked because of his research. The university, he said, has always been supportive and tolerant.

"I have felt at least some regret since before this story ever broke, and the more I thought about it, the worse I felt for some of my colleagues at Northwestern who are upset about it, including the president," he said. "It makes his job harder and the benefit to students certainly did not justify the degree to which it has hurt Northwestern at least these past few days."

Bailey said he is working with undergraduate students to arrange an event that includes "high-level discussion and debate" about the incident, and that he hopes to have Schapiro's input for the event.

CNN's Melissa Gray contributed to this report