Harrison confronted Casey S. about claims that she was still in love with an ex on Monday night (February 6), prompting her to reveal that she had broken up with the boyfriend because he didn't want marriage but she still had feelings for him.
Trading clerk Casey S. then explained the situation to Ben Flajnik, who thought she should leave Panama City and return to the US if she still wasn't over her ex-boyfriend.
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Speaking to reporters on a conference call, host Harrison said: "People made it seem like, 'How dare you just go in and kick her off the show?' That's not at all how it went down. You saw somewhat of an edited version - it was a very amicable, non-confrontational conversation.
"If Casey S. had said to me, 'Chris, you're wrong. I am head over heels in love with Ben. I don't know what you heard. Yes, I was with this guy before the show, but right now, this is it. I love this guy and I'm not giving up my chance to fall in love!' Then, case closed, and she would have been on the show and we would have never even talked to Ben."
Harrison added: "She absolutely had her half of that conversation and that led me and everybody else to understand that she said, 'Yeah, I'm not over this guy. You're right'. That is not a bad thing, but she definitely can't fall in love with Ben or marry Ben in that circumstance.
"People made it seem like it was this one-sided ambush, but that's not the way it was. She absolutely could have easily convinced me that, 'No. I'm here for the right reasons', and then no harm done and we move on to the Rose Ceremony."
Harrison admitted that the incident on last season's The Bachelorette between Ashley Hebert and Bentley Williams - who wasn't there for the right reasons - had influenced his decision to step in this time around.
"I thought with Bentley that I should have gone a little further and I regretted not telling Ashley even more," he said. "Yes, I warned Ashley and we talked to her, but I think I could have gone a little bit further in protecting her.
> Chris Harrison: 'It was right for Casey S. to leave'
"The Casey S. situation was completely different than the Bentley situation. I don't think she came on to deceive or had any ulterior motives - her motives were quite innocent. She was just trying to move on from this guy whom she didn't want to end up with, but, at the same time, it was definitely worth going in and talking to her."
Harrison told reporters that he hadn't discussed the episode with Flajnik, but he predicted the winemaker would have "a little regret" at how he handled the whole incident.
However, he pointed out that Flahnik had been blindsided by the news.
"That situation was literally thrust upon him. We showed up, knocked on his door out of nowhere, and he's hit with this information. Had he a chance to maybe go back and watch it again and rewind, he would probably be a little bit more affectionate and a little more giving to her," he said.
"I think he was a little offended and taken aback and kind of took it as an affront to him, and I don't think he quite heard everything she was saying and how sincere she was. I think he took it as, 'You have a boyfriend and you're here?' But that wasn't the story."
The Bachelor airs Mondays at 8/7c on ABC