The actual source from where Rav Nahman [Breslov] (LeM vol I ch 12 annd 28 ) brings the idea of Torah scholars that are demons does not say that exact idea. The actual Zohar [Parshat Pinchas] does say there are demons that are expert in Torah. But then Rav Nahman deduces that since there are Jewish demons and Gentile demons thus it seems that these demons can enter into people and take over their minds and souls. Actually there are plenty of examples as we know about some murderers that actually feel that their minds were taken over. 

The problem with demonic Torah scholars I think is that they ruin the reputation of Torah when it becomes clear to people what they actually are under the fancy clothing and pretense. [This is think is the reason you see this subject raised in the LeM  so many times.--Not however always in the same way. Sometimes he talks about מפרסמים של שקר famous religious leaders that are deceivers. Sometimes he talks about not giving authority to those who are not fit. 

My impression is that if people would simply pay attention to the signature of the Gra on the famous letter of excommunication and to Rav Shach, they they would be better off. After all the general Litvak yeshiva world is about straight Torah with no pretenses or claims. What you see is what you get.

[There is no question that Rav Nachman undderstands that there are demonic forces in the world a a large portion of them occupy the souls of people that look and act like Torah scholars. Thee is however a way to be saved from them and that is by  faith in the wise. That is to believe that the Gra must have had some reason for putting his signature on the letter of excommunication even if we may not understand the reason right now. --However I think I can see the reason. The Gra saw through the façade of deception.