For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
The early churches had to refer back to the Apostles, to scripture, and to the Holy Spirit, for clarity in teaching. The Apostles worked endlessly, correcting and keeping the many scattered church groups on the one true path.
I think that we need to stay in fellowship with the larger church, which helps keep us accurate on the teaching of scripture, and keeps us tied into the main body of Believers, the church, which is the "body of Christ". Learning and worshiping God in small groups is just as healthy and pure as if done in larger groups. Jesus said "anywhere two or more gather in my name....." In doing so, we do it as part of the main body of Christ, for example when we gather as a family, perhaps with neighbors, to grow in God, on a Wednesday night. We gather in God's name, in a smaller group, as part of the body of Christ, the Church. I would not want to separate myself from the general body of Believers. We are all fallible to some degree, and we need to realize and accept this basic fact. We need to deal with the fact that we will experience error in others and in ourselves. In dealing with the issue, we rely on the Holy Spirit and God's Word, along with the fellowship of many other Believers, in the main Body of Christ. Together we can keep God's Word pure, separately it seems we fail.