Not trying to start an argument here, but you watched him unload the firearm and verify clear, and then called him on muzzle sweeping his arm with an empty firearm you watched him unload?
I understand the concept of treat every firearm as loaded and practice it as well, but why would you do that?
Because it should have been a DQ under the rules. At any USPSA, Steel Challenge, or Multigun match, if you sweep yourself it is a DQ. We aren't going to check to see if the gun is loaded first, nor do we care. If you can't control the gun well enough to make sure that it doesn't point at your body, we aren't going to wait until you load it and point it at your body to say "Ok, time to stop!"
Similar to reloading with the finger on the trigger. If you do this but don't pull the trigger, the gun won't go off. However, we are going to DQ you anyway---because if you keep your finger on the trigger while reloading, you WILL pop one off sometime. And we aren't going to wait until that happens to tell you that you aren't being safe. (Nor are we going to wait until you put one over the berm into someone's field.)
If you do something unsafe, we are going to stop you before "unsafe" becomes "medical emergency."
Additionally:
How many times have you heard about someone getting shot by accident when the guy holding the gun later said "I thought it was unloaded!"
It is amazing how many people get shot by unloaded guns each year. Matter of fact, just Google "accidental shooting" and see how many people are shot each year by people who are just SURE the gun is empty.
If you don't ingrain safety habits such that you use them
ALL of the time, you WILL end up in error. In USPSA, Multigun, and Steel Challenge matches, you don't sweep yourself. Period.
If you never sweep yourself, then you'll never shoot yourself. Especially with an "unloaded" gun.
I've seen a LOT of people who think that the safety rules change as long as you have an "unloaded gun". I find that most of those people are NOT safe when the gun is loaded, either. (Because they've been sloppy in their practice, and they have NOT ingrained safety as an automatic, normal matter of course.) These are the people that make you cringe every time you see them at the range.
If people think this is too much Safety Nazi stuff, that's fine---go ahead and do what you want, safety-wise. You won't be able to shoot any competitions, though. And I won't want to ever shoot with you, either. If a person decides that safety is something that they can be lax about, then at some point in time, they are going to shoot someone.
If they shoot themselves, that's pretty much a logical consequence. But I don't want to be around them and have them shoot ME.
Quite frankly, I don't think this is a silly rule at all. Again---if you don't have sufficient muzzle control to
not point the gun at yourself, why should we wait until you actually shoot yourself to point out your safety issue?