Cracked91,
I strongly suggest, that before you ever go on a fishing trip or a hike or a camping trip, you take a course or three in armed self defense, including instruction on how to judge a situation and how to react properly before needing to draw and possibly fire your weapon. The scenario as described by you is very indicative that you are unaware of how to properly react and then act once such a situation may arise and that you do not even know what signs to look for that an attack may be imminent and therefore you would testify, in essence, against yourself if you ever went to trial and decided to take the stand. Just to have drawn your gun because someone walked up to within 21 feet of you, without you doing anything else to take precautions and to avoid trouble, except telling him to stop, is very telling that you are not knowledgeable enough about: self defense, the legality of when you may threaten someone with deadly force, what to do if you perceive a threat, what constitutes a potential threat, how to describe the threat, how to react to a threat, how to change reaction into action, and by extension - when you can use deadly force.
Sure, in the scenario as first described, you should have your hackles up but draw your gun? There were a lot of other things you could have and should have done had you been in a situation like that before drawing a firearm. Commanding someone to stop may be one of them, but why didn't the person in your made up scenario move to safety, move to put cover between himself and the other person, describe what else about the guy such as height, weight, actions such as avoiding eye contact but always watching your hands and your gun (before you drew), crouching a bit as walking as if stalking you, clenched fist or clenching and opening and clenching again, long steps, or short very determined steps, walking quietly even though the ground was littered with dry twigs and other debris, hands up in a ready to fight position as opposed to him with hands folded twiddling his thumbs, what he did when you moved (if you moved did he adjust to keep coming at you), what he did when you started to walk away faster (if you did walk away faster, did he speed up).
Your scenario is seemingly that of a scared person, a very scared person who thinks the gun is the answer to everything as you described. The fact is, as others have mentioned, there could be many reasons this guy was approaching you other than with nefarious intent. For you to think up such a situation and for you to allow the scenario to develop to the point that it did, without the person who felt endangered first having made numerous other observations and assessments and without that person having taken appropriate other actions before drawing, shows me that you are ill prepared to be in such a situation. That may sound harsh but the reality is based upon what you have told us and if that is truly the way you think, I believe you need to get a better education about being an armed citizen than you could do at this forum. I also base my assessment upon well over 30 years of carrying a firearm for self defense, several training courses I have taken, several articles I have read by experts in the field of firearms and self defense, several real life situations I have read about in the news, situations I have winessed first hand, situations that have arisen both on and off my job, having been in several situations wherein I realized I was in danger, having also been in situations where I realized I was not only in some type of possible danger but that I was about to be seriously harmed or possibly killed if I did not act properly, having been in several situations where I had to fight actually to protect myself - including using weapons to defend myself, and including once having to shoot someone. Based on all that and what I can assess of your mindset as evidenced by your scenario, and your follow-up post, I strongly recommend you take some good self defense with firearms courses, or that at least you read some good self defense with firearms books, ones that cover the basics of how to recognize danger, how to avoid it if possible, if not then how to react to it, whether or not you should go to your gun or something else first, how to act to take control of the situation legally and safely.
All the best,
Glenn B