I can't really say that Peoria has been a cultural touchstone for humorless reactionary behavior..
I grew up in a small suburb of Peoria.. lived in the area most of my life, so I know a few things about the city. The "Will it play in Peoria" statement dates back to the Vaudeville days, where Peoria was, at the time, the measure of "average joe american" entertainment preferences.
The town is many things.. some good, some bad. I can't say "humorless" though (we did give the world Richard Pryor). or even terribly "reactionary" compared to some places..(I haven't heard of any 5 year olds getting expelled or suspended for drawing a picture of a gun or a knife here yet..)
I will say one particularly negative thing about Peoria that materially impacts understanding the story in question.
"The town is a cesspit of corruption."
Seriously. Most people in the world think Chicago is bad in terms of that.. Well, Peoria gives them a significant run for their money.. just on a smaller scale. Everything bad about government... graft, double standards, backroom dirty deals, criminal complicity of the police force and prosecutors, extortion, organized crime, members of city government and their friends getting free passes on criminal activity, journalistic collusion...
It all goes on here in spades. You can't get a city contract unless you're buddy buddy with somebody with influence, scratch somebody's back, or hand them cash under the table. We have judges, prosecutors and cops openly snorting cocaine in downtown bars, sometimes with city council members.. parties at the big downtown hotels with hookers and blow and prominent citizens..
The police dept and the media collude with city hall to underreport crime.. I know of at least a dozen murders that have happened since the first of the year that have received no mention in any of the local press.. all to reduce the damage that accurate accounting of the city's crime rates would do to the city's reputation..
Why is that important? Because how how *filthy* city politics has been in Peoria for decades, nobody gets elected in this town without two things.. first, being dirty to the bone, and second, having a deep belief that they are entitled to a very different standard of treatment than the rest of society.
It's very much a "Legal? Who gives a sh*t. I'm the law in this town." kinda thing.