Nicolaitans

Let my servant Newel K. Whitney be ashamed of the Nicolaitane band and of all their secret abominations, and of all his littleness of soul before me, saith the Lord, and come up to the land of Adam-ondi-Ahman, and be a bishop unto my people, saith the Lord, not in name but in deed, saith the Lord.
And the saying pleased the whole multitude: and they chose Stephen, a man full of faith and of the Holy Ghost, and Philip, and Prochorus, and Nicanor, and Timon, and Parmenas, and Nicolas a proselyte of Antioch:
6) But this thou hast, that thou hatest the deeds of the Nicolaitans, which I also hate.
15) So hast thou also them that hold the doctrine of the Nicolaitans, which thing I hate.

Nicolaitans

The specifics of the heresy of the Nicolaitans seems to be that they believed it was OK to eat things sacrificed to idols, and that they allowed some heathen sexual practices (eg. participating in orgies, wife sharing) that were forbidden by the church.

Exegesis on the reference in D&C 117 seems to suggest that the term was being used to refer to a spirit of wanting to be in the church, but of the world. That is, having one's name on the role, but adopting the viewpoint and practices of worldly philosophy. It can be a difficult trap to avoid as we are influenced by the world we live in, and our view of what is acceptable is significantly affected by worldly philosophy. Worldly philosophy is not anchored to God and truth except inasmuch as imperfect people are dedicated to that principle. Even then, it is more like chasing truth, rather than being anchored to it. Even still, false doctrines exist in the church, penetrating from the outside, stemming from pride within the church, or stemming from errors. Worldiness and error exist within and hence, it is tempting to judge the difference between the church's doctrines and the currently popular philosophies of the world, as being solely attributable to errors within the church rather than our own errors and the errors of the world. Considering how the church is anchored to the rock of revelation, this would be a bad assumption.

Cross-references