KJVO is a guilt-by-association insult.
If you have someone who claims to be KJVO, whether you know what they mean by it or not, you (esp. the OP's disingenuous author) can level at them all manner of assumptive accusations, forcing them to defend themselves rather than address issues.
For instance, Ruckman and Riplinger.
Neither are defendable, yet any "kjvo" is forced to answer for their folly.
Rather than narrow down the specifics of someone's actual beliefs, the hurler of the op's insult is safe to cherry-pick and play whack-a-mole with the intended victim, constantly hammering them with assumptions.
Since we all know there is no definition to "KJVO", the use of it is most assuredly playground bullying, and nothing more.