My point was having beer at the range. I thought that was pretty clear. The amount is inconsequential, I purposely used a ridiculously small amount as a demonstration.
My point is that no one is ever at 100% to begin with. You're always impaired to some extent. If you're talking to someone, distracted, not feeling well, tired, or taking Benadryl, you're already impaired to some extent. Your range says no alcohol whatsoever, because they have to draw the line somewhere, not because having a beer or two makes you unsafe.
There are plenty of reasons to abstain from drinking any amount of alcohol while carrying. Liability would be one. Maybe you're one of those people who just can't stop when you've had one beer. It could be illegal in your state. But I don't see it as inherently unsafe to have a small level of alcohol in your system.