The last I knew, idolatry is worship to a person or organization. And, when they are in accordance with "God's spirit-directed organization", they are effectively worshiping that organization. Just observe what happens when that organization creates new doctrine that is not backed by the Bible, or worse yet, blatantly contradicts it. People will go by the organization before the Bible--which is the Bible definition of idolatry.
Which is made serious when they claim to be the only ones that follow the Bible.