I call them people enjoying a public park. Yes, some are idiots, but there are idiots anywhere you go in this world. I just make sure to pay extra attention to people throwing, pick up any trash I see, and be prepared to skip a hole here or there or wait (oh darn, I have to stand around outside enjoying nature...).
More importantly, I'm thankful for chuckers as they are the ones who buy the vast majority of discs that allow disc companies to have money to produce new molds, sponsor tournaments and players and generally keep the sport growing.
Just my $.02