I think what you did was great Londondrz, but not sure I'd feel able to do the same on my own.
In saying that I have stepped in to help people in the past when I thought they were being threatened. I also helped a girl who was being harrassed at a cashpoint, but I had my partner with me.
Losers like this need to be challenged about their littering I agree, but as Roz says, I wouldn't put myself in danger over it.
It worries me if it's becoming the official line that people should step in over littering. The thing is, you never know when someone could pull a knife on you, but I do appreciate people like you out there who are willing to stand up for others.