All self-proclaimed body language experts I know in real life, turn out, in fact, are really great at noticing body movements, even the slightest one. Only the downside is they have very little to no access to the mind. Not just the minds of people they record every movement of, but their own.
Apparently when you don't care for people you don't like, and keep the ones that you trust, you don't have to read their body language just to survive. Not that it would ever improve or become true when you do.
The question is, people who practice that kind of rationalization, what do they do that for?
The advantage of being great at rationalization and being paranoid is, you can choose whatever option that benefits you the most at that moment, then pick the evidence later. And there are theories for everything. If you take advantage of someone, that's because their body language says they betray you first therefore you just do what's needed to protect yourself. You are not a bad person!
Being paranoid and rationalization go together, because you will always need to reassure yourself that you are not paranoid. But then it doesn't reflect true reality. Something makes sense at the moment, will contradict later with further evidence. So it's a constant denial of reality where feeling is put above anything fact, just so they don't have to face contradictions.