This is from the Economist (Jan 3, 2015). (You can see the full article here - http://www.economist.com/news/united-states/21637401-what-ceaseless-rows-over-yellowstone-national-park-reveal-about-america-ranchers-v)
Behind that local clash — pitting folk with gun racks on their trucks against those with bike racks, as Mr Farrell puts it — there lurks a still larger suspicion of the federal government.
What does "pitting...folk" mean here? And is this expression used frequently?
Does 'suspicion' here have different meaning with 'doubt'?