הלא יראתך כסילתיך Is not your fear (of God) your stupidity.  Too many books nowadays claim to be teaching fear of God but are in fact the product of diseased imaginations, [and for this reason the Gra signed the letter of excommunication]. The idea is to cancel books that claim to be teaching Torah but are in fact the opposite. However the Gra is ignored.  

That is the exact reason the Musar movement of Rav Israel Salanter emphasized specifically the books of fear of God of the Middle ages before all the diseased books of later days infected the religious world