I find campgrounds to be more dangerous than boondocking it in the middle of nowhere, personally. I've camped alone and with my girlfriend in many places, everywhere from KOAs to state parks to a truck stop parking lot. I've only felt even slightly uncomfortable twice, once in a KOA of all places, and once in a very large campground that was more mobile home park than campground. I've never felt uncomfortable in the mountains, even when I'm the only person for tens of miles.
Even at the places that made me uncomfortable, I worried more about the beer being stolen from my cooler than violence against me.
A lot of this probably depends on where people live, and what they are used to (studies confirm this: people generally rank risky behavior as less risky when familiar, more risky when it is unfamiliar - hense why people often worry more about getting onto a jet airplane than into their own car, despite the car being far more riskier). I'm much more used to, having grown up in Wyoming, to wide open spaces and few people around - so it makes sense I'd get a little nervous sometimes when hundreds of people share a couple acres of land at a campground, but not when I have a couple hundred acres to myself.