Herman Cain, Republican presidential candidate, on Thursday night refused to expand on why he believes being gay is a choice.

The 65-year-old Cain made his remarks during an appearance on MSNBC's The Last Word with Lawrence O'Donnell.

When host Lawrence O'Donnell pitched a question submitted via Twitter that referred to Cain's previous statements on ABC's The View, Cain refused to answer the question.

On The View, Cain agreed to a list of conservative positions rattled off by co-host Joy Behar, including his opposition to gay marriage, his belief that “Don't Ask, Don't Tell,” the policy which ended on September 20 that banned gay and bisexual troops from serving openly, should be reinstated, and his belief that being gay is a choice.

“I don't think anybody in this world wants to be gay considering all the vilification that is brought upon someone who is gay. Why would you choose that?” Behar asked.

“Well, you show me the science that says that it's not and I could be persuaded,” Cain responded, then added, otherwise it's “just a difference of opinion.”

On The Last Word, the viewer wanted to know if Cain had chosen to be straight.

“Lawrence, there will always be a difference of opinion,” Cain said. “Like I told Joy Behar. She has her opinion, I have my opinion. It's a difference of opinion. Next question, please.” (The video is embedded in the right panel of this page.)

(Related: Herman Cain's choice not to be gay praised by Stephen Colbert.)