It wasn't just the cries of "Bitch!" (for Hillary Clinton) or, "The gays had it coming" (for the Orlando shooting victims) that rattled Sexton. It wasn't even that he heard "more than a few" in Trump's audience hurl racial epithets and encourage anti-Trump protesters to kill themselves.
"I surprised by the casualness and joy they took in their hatred," said Sexton.
To Sexton, who has made something of a study of Trump rallies, Tuesday marked a turning point. He had attended four previous Trump events since he began following presidential campaigns from both parties last year.
The event "was the first time I walked away with the idea that maybe it’s not as simple as, 'He’s the ringleader,'" Sexton said in phone interview. "I’m starting to wonder if he’s not the one behind the wheel."
Sexton tweeted his observations of the rally as he lined up with other attendees outside. Twitter soon made made his tweets into a Moment -- a curated feed from an event -- which gave users a glimpse inside the rally through Sexton's eyes.
(See Sexton's full timeline of the Trump rally below.)
Sexton, a creative writing professor, said he holds his working-class roots in southern Indiana "very near and dear to my heart." He said he recognizes his family and himself in many of Trump's supporters.
That's why he wanted to "go an extra step" to try to understand Trump's aggressive backers.
"I can understand why, maybe in the beginning, working-class people flocked to Trump," Sexton said. "To put in clumsily, he was almost an antidote to a 'politically correct' culture a lot of people found stifling and dangerous."
Trump despises what he calls political correctness, and has made bold but vague proclamations of jobs, wealth and greatness aimed at a segment of the population that feels marginalized by a progressive agenda. That makes him an appealing leader figure to whom supporters can "take their frustrations, economically and socially," Sexton said.
The worst of the rhetoric that circulates at Trump events can be divided into two general categories, Sexton said.
"One I would describe as a casual country club-like hate," Sexton said. "Trump events are outlets for people to come out and engage in hatred that society has kind of pushed aside -- and they kind of revel in it.
"There's another side that’s kind of nihilistic — like wanting to burn everything down," Sexton said. "I don’t know if it was cathartic or symptomatic. But it was obvious that so many were feeling it."
Sexton was quick to point out that not all Trump supporters espoused such views, and he doesn't broad-stroke all of the candidate's followers as hateful bigots, racists and misogynists.
Loyalty, he noted, has long been a core tenet of the Republican Party, and likely what keeps much of the party's "old guard" engaged in the campaign.
"They’re conservative. They care about their country. Maybe you don’t agree with their social beliefs or even their economic beliefs, but you can at least say ‘they’re a civil person,'" Sexton said.
"But I see a lot of them at these Trump things, and at times I can catch a flicker in their eyes of, 'What am I doing here? What is this and how did I get here?'"
Trump, Sexton said, has created a "strange, reality-bending political correctness-free zone."
"So afterwards, his supporters feel justified," he said. "It's like a collegial, ‘We’re all here enjoying this Donald Trump rally, and it’s great we can be ourselves.'"
Sexton described the most engaged rally-goers as seeming almost shocked that there were protesters in their midst. He claimed at one point, a supporter asked people in the audience to crowd to clap if they agreed with that Trump was saying as a way to sniff out who was a genuine supporter and who was an interloper.
"People looked at protesters, stripped them of their humanity, and had a desire to do them actual harm," Sexton said. "And I don’t think there are few of them."
Sexton, after previous Trump rallies, wrote that he wouldn't be surprised if someone dies at a Trump event before the campaign is over.
"These people were comfortable in their anger," he said.
By now, Sexton said he's unconvinced that Trump believes some of what he's saying. He's even gone back to watch old Trump interviews and appearances to compare positions that now seem relatively moderate to Trump's current demagogic views.
"I think this is a matter of opportunism. Maybe he’s tricked himself into believing he thinks these things," Sexton said.
As for Trump's supporters, Sexton said he thinks many back Trump more as an excuse than as a candidate.
“I wanted really, really, badly to at least afford [Trump supporters] empathy," Sexton said. "But there’s something else going on here. There’s some kind of ugliness in these people. I’m not sure if they’re nihilistic or more violent than other people. I’m not sure if sure if they’ve gone beyond anger to the other side of rationality."
During his five-hour drive back to Georgia after the rally, Sexton reflected on what he said frightens him the most about what he witnessed.
"What I can’t get out of my head is that while Donald Trump will likely be defeated, that’s not going to make these people go away," he said.
"They’re not going to pack up their bags and go home; they’re here. And I’m afraid this sort of provocation is going to amount to something more."
Editor's note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims -- 1.6 billion members of an entire religion -- from entering the U.S.