These deer were 600yds from me I'd guess. The photo doesn't begin to do the scene justice but you could see these deer plain as day. I know people that I think could hit one with open sights shooting offhand. Not me.
However laying prone, rifle on bipod and with a scope at 8-16 power I'd attempt the shot and I believe I would have a very good chance of an ethical kill.
If you're going to attempt that shot, you had better do more than guess at the range. I agree that many would have a good chance of killing the animal. But there is also some chance that the deer would be gut shot or hit in some other nonvital place and left to die. In my mind, ethics means weighing the odds and maybe passing up a questionable shot.
There might be people who could consistently hit a deer at 600 yards standing. They are all in the Olympics.