<human>: Can you give me the gist of the text in a nutshell?

The question comes from an experience I had yesterday- a group of friends and I get together a couple of times a week in the evening (8:30 until about 10:30ish, i.e. it's dark) to play ultimate frisbee. The field we play on is surrounded by tennis courts and is kind of lit up by the lights on those courts well enough to play but not well enough that shady stuff doesn't happen there from time to time. 

Yesterday some random guy who had just finished a tennis game joined our ultimate game for the last half hour. As we finished up a few people lingered just to chat for a bit, which generally happens. Usually I just roll out pretty quickly but the guy that we didn't know was staying and chatting with a couple of the girls that are regulars, so I stayed just to make sure he wasn't a rapist or didn't try anything. He seemed like a pretty nice guy, but you never really know, right?

As I eventually drove away I thought that the fact that I felt I needed to stay said something about my lack of faith in people. Was I justified?
<bot>: I stayed longer than usual with some female friends in a semi-shady part of town so they didn't get raped by strangers.