Its a horrible situation, but the main problem of the whole situation is that there is NO way to appeal this NCOER, based on the fact that an investigation into the EO violation has already happened, and the BN commander found the complaint to be valid.
The NCO could always try and have the EO complaint reviewd, but the chances that a different individual would go against the BN commander without NEW and COMPELLING evidence, pretty much means this NCO is out of luck.
The fact that the NCO now has an EO violation in his records (at least at the unit level) means that he almost certainly WILL REQUIRE a NO in his/her Army Values block, and this is deservedly so. Having a NO in your Army Values is THE BEST way to ensure you don’t get picked up for SFC anytime soon.
There is an appeals process, and you can read up on it, however, with a validated EO violation on file, there is almost NO way this would get overturned. Sorry to burst the Hope Bubble.