Being over deferential. There have been many great thinkers in history and it can be tempting to treat anything whatsoever said by a thinker whom you greatly admire as if it were obviously true ('faithful and discreet slave' must be right on everything because they have a great knowledge of scripture?). Sometimes there may be excellent reasons for relying on the opinions of experts and the authority of those who have devoted their lifetime to the study of a particular subject. However, this attitude can be taken too far and degenerate into obseqiousness and excessive humility, which gets in the way of critical thought (JW's idolising the 'faithful and discreet slave' class and the Organisation as a whole, putting it ahead of). Kowting means, literally, touching the ground with one's forehead as a sign of deference.
For instance, even though Friedrich Nietzsche had many interesting and profound thoughts on a range of subjects, it would be merely kowtowing to him to take seriously his pronouncements on women (he famously declared, 'When thou goest to a woman take they whip'), just because he is a thinker whom you respect. Uncritical acceptance of other people's ideas leads to mental stagnation (stagnation is surely evident within the Organisation).