Bryan Derksen wrote:
[...] I think that he's spent so much time fighting vandals and POV-pushers that he no longer recognizes that anyone not completely on "his side" isn't necessarily one themselves. Since he's taking such an absolutist approach in his interpretation of the guideline in question it doesn't leave much, and it's made him thoroughly entrenched against any consideration that he might be incorrect.
Something I deal with a lot professionally is people who are burning out on their work. Sounds like this guy is in that category.
If he's already seeing you as an antagonist, it will be hard for you to reach him yourself. You seem like a pretty relaxed guy, so you may be doing this already, but I'd encourage you to avoid rising to any of his challenging behavior, as that will, from his perspective, justify his defensiveness.
If he's not too burnt, a change of scenery may do him a lot of good. Perhaps some mediator can arrange a deal where some people he trusts take over what he sees as his territory, so that he can take a break. Even if he works on other articles or other tasks, that may be enough to get him to relax and be reasonable again.
Beyond that, an actual break would help more. I know how to persuade people of that in a workplace setting, but I can't think of a way to approach that on Wikipedia that couldn't be taken as a veiled threat. Hopefully one of his on-wiki pals will take him aside and get him to focus on staying a healthy long-term contributor.
William