Vietnam veteran Geoff Thomas loves his gay son, Nathan, and wanted to make his support known. So the Australian plumber blanketed his electric-blue utility vehicle with pro-LGBT stickers.

"I was conditioned to be homophobic, and then one day my son comes out to me," Thomas, who lives in Sydney, told Buzzfeed. "I had to ask myself the question, 'What is it about gays that I didn't like?' After that, I decided it was unfounded fear, ignorance and prejudice."

Realizing that his son still wasn't equal under Australian law, "really got up my nose," he says. And inspired him to become a staunch advocate for marriage equality Down Under.

"I'd had this talk with some people, and I said, 'Every man and his dog supports marriage equality,'" Thomas said, "And I thought, 'I'll put that on my ute!'"

The car is also emblazoned with stickers for PFLAG and encouragements to "call your MP and senator today," to push for same-sex marriage in Australia. To make sure his message is seen nationwide, Thomas is currently embarking on a road trip through Melbourne, Mount Gambia and the Riverina region, and having as many conversations as possible about equality.

"To me, it's a civil rights issue," Thomas says. "It's got nothing to do with religion, nothing to do with gay people having babies. In the 12 years I've been advocating for this, I've yet to hear a reasonable argument against it."

Thomas became something of a national figurehead for the cause when he appeared on the current affairs program Q&A in 2010 and challenged then-MP Tony Abbott on the topic. "I have a gay son," he told the future Prime Minister. "When I was confronted with that situation, in a very short amount of time and with due consideration, I accepted his position and I overcame my ignorance and fear of gays and the idea of gay marriage. When will you, Mr. Abbott?"

For his part, Nathan is thrilled with his dad's support.

"I didn't even know gay really existed when I was younger," he revealed on the radio show Compass. "I know Dad doesn't like it now, but he used to say 'Plumbers aren't poofs or wimps.' Gay really wasn't an option in our household... It was hugely hard."

But even at the start, Geoff chose his son over his prejudices. "I did say to my son shortly after we started our conversation that I would have to obviously look at my attitudes. And I have—and it hasn't been difficult."

"It's a simple matter of treating gay people like anybody else," he adds. "We need to be treating everybody in this country equally."

Follow Geoff Thomas's equality road trip on Twitter.