Luke, however, broached the subject with Dr. Pepper before ever mentioning the concern to his wife, who also appeared on the Unfiltered special along with her MAFS co-star Kristine Killingsworth.
"I don't think Luke is an honest guy," Dr. Pepper told Jamie.
"I was very much taken with him when we first interviewed him. He's creative and smart and charming and all kinds of good things I thought would be perfect for Kate."
Dr. Pepper, however, changed her tone and said, "But when we ask him about these kinds of things, he's evasive."
Dr. Pepper addressed Kate and noted, "He doesn't really tell you how he's feeling. He's trying to squirrel out of it, and the fact I knew something about her that she didn't know struck me as a major violation of what a marriage is."
Kate considers herself a social drinker, but she acknowledged on Unfiltered "it's possible" she might have been drinking more during the beginning stages of her marriage in order to relieve some anxiety given her dynamic with Luke was often uncomfortable and stressful.
As Married at First Sight viewers recall, Luke did not find himself physically attracted to Kate, and when they shared their first post-wedding kiss, he told his wife he felt "repulsed" and "dead inside."
When Jamie asked Dr. Pepper what she thought was going on with Luke, the expert replied, "I have to describe the behavior as manipulative. It's hot and cold, reward and punishment... angry and nasty yet sweet. What's going on?!"
"That's the kind of thing that's always destructive," Dr. Pepper pointed out.
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"I think Luke is an assh-le," Kristine replied, which prompted Kate and Dr. Pepper to burst into laughter. "I don't know how else you could possibly put it!"
"We all come into these circumstances wanting love and wanting this strong marriage, and we're excited to meet whoever we're going to be with. Even if they're not exactly what you wanted, you don't put them down -- or you find a better way to say things, especially to your wife," Kristine explained.
Kate confessed on Unfiltered she lost all trust in Luke after his comment about her drinking and so they took a major step back in their marriage.
"I'm worried Luke is not going to say what he really thinks," Dr. Pepper shared.
"I'm also a little worried Kate doesn't stand up for herself. I think it's appropriate, if you're not getting the respect and if your trust is not being served, to ask more and hold your husband accountable."