His classroom is hung with plastic human skulls and skeletons (he took one down after feeling the place might be getting too morbid), and a wooden coffin stands in a rear corner. A student once hid inside it, emerging when class was well under way to scare his teacher and classmates half to death.
"Teenagers are convinced that they're immortal and invincible," Seyler says, explaining the ghoulish kitsch. "I want to remind them that life is short."
And that eternity is long.
Seyler illustrates just how long with a ball of blue yarn.
It's a sunny Sunday morning in early August, and he is standing in front of 20 kids in a different classroom, leading a Sunday school class for Grandview Park Baptist Church.
Seyler asks for volunteers, and a grove of eager hands shoots up. A boy with an Afro is soon following Seyler's instructions to pull one end of the yarn to a corner of the room. Seyler asks another kid to pull the yarn to the next corner, forming a giant L.
Before long, all the children are up from their seats and stationed around the edges of the room, each doing his or her part to form a rectangle of blue string about 100 feet long.
When the yarn is completely unspooled, Seyler holds up his end, wrapped in an inch of white athletic tape.
He explains to a room of first- through fifth-graders that this short length of taped string represents a human lifespan on Earth, while the rest represents the time we spend in eternity, after death.
"When we die, we go to heaven or hell," Seyler tells them. "We have a lot more to live after we die, but lots of people just focus on this little piece."
The only way to get to heaven, he continues, is to accept Jesus as savior, to recognize that he took on our sins and died for them: "I love Jesus more than my own life; that's how tight we are."
"I love Jesus more than my own kids," he says a moment later, catching the eye of his 9-year-old, Jack, who is seated in the front row.
None of Seyler's teachings about eternity or hell comes even close to resembling a political statement. Yet they go a long way in explaining how a born-again Christian could have such deep reservations about a Mormon candidate.
In Seyler's view, getting it right when it comes to God and Jesus is a high-stakes business, the difference between spending eternity in heaven vs. hell. So why would he trust the country with someone whose beliefs are shaped not just by the Bible but also by another text, the Book of Mormon?
Never mind that Mormons consider themselves Christians and focus intensely on Jesus, starting with the official name of their church: the Church of Jesus Christ of Latter-day Saints. For Seyler, that just makes a Romney presidency even more dangerous.
"People will say he seems like such an upstanding guy; how could he be wrong" about religion, Seyler says, sitting at Fazoli's, an Italian fast-food chain, with his family after church. His blond-haired 4-year-old, William, is pulling a rip cord that sends his new Buzz Lightyear toy skating across the table.
"If he becomes president, how much of a soapbox for his religion will he have?"
Questions about Romney's devout Mormon faith have dogged his campaign from day one. In this year's Republican primaries, the GOP's evangelical base broke against Romney, fueling former Sen. Rick Santorum's insurgent campaign.
Recent polling shows that most evangelicals now back Romney, regardless of whether they're comfortable with his faith. A September Pew survey found that more than three-quarters of registered white evangelicals support Romney.
But a July survey from Pew found that about a quarter of white evangelicals are uncomfortable with Romney's religion -- and that only one in five in that group is strongly pro-Romney.
That could mean fewer born-again activists making phone calls and knocking on doors for Romney -- and thus fewer chances of getting someone like Seyler to turn out.
Seyler has plenty of hang-ups about Romney beyond religion. The candidate's support for abortion rights as governor of Massachusetts -- a position he reversed while in office -- makes him suspect on Seyler's No. 1 political issue.
And Seyler, who wears jeans to church and spends weekends burning old furniture in his backyard fire pit, doesn't care for Romney's uppity, buffed-to-a-high-sheen manner.
"I want to see someone who's real," he says, cutting a slice of chicken parm with a plastic knife. "Romney's squeaky clean."
Plus, as an evangelical free-thinker, Seyler is a little tired of blindly pulling the Republican lever in the voting booth. He doesn't want to necessarily accept whomever the Republican Party is handing down.