The great frat bro reckoning: Heyday or abuse? I have no regrets.

For Patrick Williams, his ideal of fraternity brotherhood was shattered before he could even be crowned a full-fledged Sigma Chi brother.“Pledging was one of the worst experiences of my life,” the 46-year-old marketing consultant told The Post about his Greek experience, which happened 25 years ago as a freshman at the University of Utah.“The sh-t that they did” — including dunking the young men in ice water until they couldn’t feel their legs, he recalled, and then forcing them to march across campus — “was bonkers.” Williams has become one of a growing number of former frat boys vocally criticizing the collegiate Greek system on social media — in the wake of a host of allegations against fraternities at Cornell, Arizona State and Penn State, where a frat house drug ring was busted in August.His hope is to shine a light on practices that derail campus life altogether, and convince young boys to steer clear of fraternities.

Before he pledged, Williams was a bright-eyed 21-year-old who was starting school just after completing a Mormon mission.Growing up hearing his family’s positive experiences in the Greek system — Williams’s father and cousins were in Sigma Chi; his mother was a Delta Gamma — he was excited to join the same frat as his family with hopes of making lifelong friends and meeting girls.“I had a lot of respect for my dad and my cousins, so I thought, ‘Hey, this would be a really cool, stand-up thing to do,’” he said.But then, Williams told The Post, the horrific pledging process began. To start, Williams and his fellow pledges were instructed to clean up “poo and pee and sh-t” in the fraternity’s then brand-new house.“They purposely threw up all over the place because they knew we were going to come in and clean it.” “We were spit at, we [got] thrown beer on us — they made us run around the campus half-naked,” said Williams.

The worst, he said, were the “Friday Night Fun” sessions where his pled...