In an interview on the ABC's Kitchen Cabinet, the Motoring Enthusiast Party senator said a fight with his wife prompted him to question his views on gay people.

"I did have very opposing views to what I have now, but that's because of 'monkey see, monkey do'," Muir explained. "You grow a up certain way, you're told certain things, you go with it."

While debating marriage equality with his wife one day, Muir said something that made him stop and think.

"We were having that [marriage] debate, and I can't even remember what my argument was but I tell you now it was weak," Muir sad.

"And she said to me, 'what if your son was to turn out to be gay?'"

"My answer was, 'I'll disown him'."

"The look on her face was just absolute sheer disgust. I thought, gee, that's a really bad thing to say."

This exchange led Muir to think on the issue for "a long time", asking himself "what's my real problem here?"