Rav Nahman says in the Le.M  vol I:72 that even in coming close to God one needs to be wary of ריבוי אור [excess light or excess excitement. ] This I think accounts for the fanaticism of the religious world

[The same theme is brought in the LeM vol II chapter 5:7 and  chapter 9] 

But in addition i thin the problem with Torah scholars that are demonsa adds to the issue. And that aspect of things is brought up a lot more in the LeM , but not in just so many words, The only times you see this in the LeM explicitly are in Lem I 12 and LeM I 28.