One thing I have noticed is that when I watch (or try to watch) various YouTube videos where the pastor or preacher is speaking against a certain heresy or errant movement, he will almost inevitably connect the KJV to it. What I mean is that the person will say that one of the reasons to reject whatever errant doctrine is being discussed is because it undermines the KJV. Usually, in my experience, this happens when Bible version/translation issues are not pertinent to the doctrinal issue at hand.
I'll just be sitting there listening to the preacher talk about the specific heresy and then he'll say something to the effect of "it goes against the King James Bible" or "don't use any of the corrupt or devil-inspired versions". At that point, I just have to stop the video and go elsewhere because I'm thinking "well you've lost my ear right there". It's like full-stop, you know?
I find that one of the indicators of someone being KJVO is if he/she makes a special point to say during the sermon or speech that the KJV is being used, especially, as I mentioned above, it really has no connection to the subject matter of the sermon or speech.