One thing you have to think about is that we have moved in on their habitat. The bear was just doing what it would usually do in the wild. What would you do if you came into contact with a bear?
I already have (while camping when I was 8). A bear walked into the campground 20-30ft away from us, coincidentally a dog named bear got loose from his owner and charged the bear. The dog was pretty big and managed to knock the bear over, then started to beat the crap out of the bear! The bear didn't know what had happened so it ran off; it was later found and reloacted farther north.