You bet, and thanks for your condolences. In short, almost certainly this doesn't apply to you.

The pattern is that in these scenarios, usually the people are quite intelligent and often accomplished. This gives them a repository of valid phrases and concepts to draw upon to breath legitimacy into their boogeymen. The evidence they present, however, is completely benign. That person, however, has quite the story they think is proven. It's literally as if they're showing you a basic electronic device w/ the cover removed and that proves all sorts of maliciousness.

Attempting to argue back is completely ineffective and even if you "win" one point, they'll quickly shift to another and nothing sticks, especially not the next time you talk to them.

I wouldn't even remotely compare this to more commonly contested topics like differing religious/political/social views, even at the extreme. This involves a visceral fear that >you< are actively being attacked, not some nefarious, shadow with a grand plan.

In my experience... a characteristic of this type of condition is a tendency for the brain to make connections too eagerly, and to jump to conclusions. His computer did something weird, therefore it must have been hacked. He heard about the Solarwinds breach in the news, therefore it must be related. He opened some files and saw Daniel's name, therefore he must be responsible. And so on.

It really is what my father does. We're very analytical in his side of the family. We're also prone to narrow view when we have 'attacks' we make huge amounts of logical connections that explains (or try to) what we suppose is happening and it's near impossible to deal with us until the storm is over. A kind of paranoid burst. Maybe not to the extent of your friend but from your words it's really similar.

Have you ever spoken to a professional? Even if you don't feel like anything is wrong, it can be a good to know yourself better. And if anything, potentially face an aspect of yourself that may otherwise surprise you later in life.

I have a very clear idea of what spectrum we're talking about here, but maybe it's better left unspecified to not influence too much (: