The place in the LeM of Rav Nahman of Breslov where he discusses the Torah of the Realm of Evil in the vol I:30. [paragraph 8].
This is tied to the idea that one needs stubbornness to merit to true Torah. But there is a sort of stubbornness and arrogance of the Dark Side. So not everyone that claims to be teaching Torah can be trusted or accepted since their Torah might be the Torah of the Sitra Achra. In fact, since we know from the Ari that the Dark Side is the majority rule in this world, so one ought to expect that most of those that claim to teach Torah are not from the Realm of Holiness. Rather they are probably teaching the Torah of the Dark Side.
According to the rules Rav Nahman gives there in that Torah lesson, it is clear that in place like the Mir and other Litvak yeshivas were there is humility, there is also true and authentic Torah.
[You could go further into this subject by pointing out that not everything that pretends to be Torah is Torah. The Rif [Rav Isaac Alfasi] explains in Sanhedrin chapter 11 "Helek" that when R.Akiva said one who reads outside books has no portion in the next world refers to books that explain the Torah but not according to midrashei chazal [ the explanations given in the Gemara and or midrashim. Some books would be OK like the books of Rav Nahman or the Or HaChaim since they are simply explaining the Torah based on the midrashim of the sages." So when it says, "Everything that even the smallest student offers" in way of explanation, that refers to explaining the Midrashim that explain the Torah. Not coming up with explanations of his own on Torah." So not everything that pretends to be Torah is Torah.]
According tp the criterion of Rav Isaac Alfasi it would be hard to a kosher book among thee religious .They all make up commentaries not based on midrahei chazal.
