I shoot on an unsupervised range at my gun club all the time, and have, on only a few occasions, witnessed rules being broken. When that happens, I believe that we all have the responsibility to politely bring the issue up with that person breaking the rules.
For example, I once witnessed people shooting fist sized rocks at 200 yards. I mentioned that is dangerous because bullets ricochet and can end up flying in the wrong direction.... the person said, "I never thought of that... the rocks are a long ways away and I never thought about that happening". If I were a prick, made him feel bad, or did not say anything at all, nothing would have been learned and something bad may have happened later.... Was he unsafe in doing that? Of course. Did he need to be belittled over it? No.
Assuming someone is an idiot IMHO is not correct. Ever had a bad day? Lots of things on your mind from work? Finding out you or a loved on was just diagnosed with cancer or another bad health condition? Many things can cause even the most responsible person to make a split second mistake. Happens on our highways every day.
At the end of they day, we all enjoy our sport, and want everyone to be safe. As hunters and shooters, alienating or being rude to others can only hurt who we are and what we do. Being polite and educating during a "teachable moment" is always good.