It seems to play right into paranoid fantasy, and perhaps precipitate it in cases, that to be ignorant of a hostile cultural reality is tagged as "mentally healthy".
I guess another way to think about it is that irrational fears remain irrational even if they turn out to be true. If you don't have a reasonable justification for your fears, then it is purely a coincidence that the fears happen to be true.
I'd say that's not another way to think about it rather than exactly what mistersquid was saying, stripped of all the psychobabble (and I say that with degree of affection for French Fraud and his ilk).
Something similar can be seen in depression. I've gone through multiple periods of depression, and I noticed quite a difference in quality between them. While it can probably not be generalized, I noticed that the stronger, more vivid and often shorter periods of depression often least matched reality in hindsight, whereas the dragging, nagging, longer periods of depression often felt justified even in hindsight. Even now, for example, I don't feel that my perspective has fundamentally changed since my last long period of depression; I just don't feel bad about it.
The fact that I felt bad about a situation that other people don't feel bad about was what made me 'someone dealing with depression', not the objective facts of my life.
Realizing this, combined with buddhist thought and practice, has made it easier for me to deal with depression, social anxiety (which often includes quite a bit of paranoia), and my changing moods in general.