There isn't really anger, but a sense of annoyance that I've actually met Geocachers who are so inconsiderate, as well as being rude, too. When I first looked into this hobby, I was amazed at how nice the people were that I was meeting, no matter where I went. I still didn't join in doing caching regularly, myself, at that time because I felt that it was only a matter of time before the jerks and airheads would start getting involved and threaten to ruin the fun for me. While there have been a vast number of the latter to participate, I have only encountered a few of the former. So you might say it's also dismay that they've finally been spotted in the three years since I've taken an interest in geocaching... and just after I was getting deeper into it, too. Three years is a long time to finally run into such ill mannered types.
As for playing nice, I'm trying to do so, but it seems you missed the point. It wasn't about no longer having fun or me not being able to play nice with others. It was about people sticking a nano - of all the sizes of caches, it's always nanos - in the dead center area of a small park instead of leaving a bit of room on one end or another for someone to place another cache. That's not only disheartening to see, it's taking away the fun for some of us who like caches that aren't just the type where you sign your name and walk along with a spring in your step like you've done something amazing.
The least they could do is make it a puzzle, or part of a multi-cache if they're going to do something so self-centered and egotistical. It would be no different than me walking into your bedroom and planting a flag in the middle of your bed while you were away from home, in many respects, rather than just putting an "Elect Joe Josephs for Mayor" on the parking strip of your front yard.