Well certainly a station in a major city will have the ability to be more selective with regard to callers. There are simply more of them than in a smaller market. I too have worked in larger, but not as large as Chicago, radio. Yes things are different. But what we don't know is if this writer may have been a producer or some other capacity in a large market and took a step down to a smaller market to become talent. In my market, unless are blacklisted, you get on the air. Some callers are just so far out that the host won't even take the call. (I'm in top 30-40 market). Even our dominant AM will take all callers with the exception of the blacklisted folks or the comment has nothing to do with the topic. In a small market setting, probably the kook makes it to the air.
This guys analysis of the national shows is pretty close. Maybe not 100%, but a good summarization.
If you're ever in Chicago, visit the WGN Radio studios. They are a good example of a top 10 market news-talk station.
Even if you've worked major market radio before, it's a good eye-opener.
I graduated to Chicago from St. Louis and we thought we knew what it was all about in St.Louis.....wrongo!
I started in radio in 1959 and went from Des Moines - Omaha - Kansas City - St. Louis - Chicago. Left radio for TV in 1985 and retired from TV last year. Throughout that time period, WGN has remained essentially the same except for equipment, of course. They used to even build their own transmitters (for themselves and other stations) as they owned Continental....don't know if the still do. Their studios are like "Radio Valhalla".