Does this not explain, at least somewhat, what is transpiring in Boston, KY?

Let us note, from the first, that traditional Christianity is a balance of doctrines, and not merely of doctrines but of emphases. You must not exaggerate in either direction, or the balance is disturbed. An excellent thing to abandon yourself, without reserve, into God's hands; if your own rhetoric leads you into fantastic expressions of the idea, there is no great harm done. But, teach on principle that it is an infidelity to wonder whether you are saved or lost, and you have overweighted your whole devotional structure; you have ruled out a whole type of religious self-expression. Conversely, it is a holy thing to trust in the redeeming merits of Christ. But, put it about that such confidence is the indispensable sign of being in God's favour, that, unless and until he is experimentally aware of it, a man is lost, and the balance has been disturbed at the opposite end; you have condemned one type of religious mind to despair.

- Msgr. Ronald Knox, Enthusiasm, p. 580-1

Obscurus is right.

Basically, it means that even if a person/group isn't making up "new" doctrines or spouting outright heresy, just focusing TOO MUCH on one doctrine can throw everything off balance and lead to error.

Focusing too much on the need for priests/ the Mass and you might be tempted to run a seminary that is utterly unfit and unworthy for the task, one that does more harm than good. Being downplayed is the fact that God will provide, and He will never require you to use evil means (pablo? dissimulation? deception? rogue pseudo-bishops?) to get that which we need (preists).

A similar point, equally interesting (that I learned in the seminary) was the dual need of

DOCTRINE
and
LIVES OF THE SAINTS

You need both.

If you focus too much on Lives of the Saints, you start to think that the extraordinary should be expected as ordinary. You also might focus too much on emotion and not enough on reason. You would be seeking out what kind of extraordinary saint you are going to be, rather than doing your boring old duty of state which is the ordinary means of salvation.

If you focus too much on doctrine, you forget that God is master of his gifts, and can make exceptions, visit people, give special graces, etc. In general, in this case you would be too cold, trying to be exclusively "reason" and forgetting emotion, charity, etc.

Exactly, Matthew. The temptation is going to be to focus too much on one issue which will then throw off balance the entire edifice of the faith. Prudence and proper discernment then are rejected. This is a classic case of the end justifying the means which is a VERY un-Catholic principle.

End - Purity of Doctrine (A Good thing)
Means - Accepting of vagus "bishops", condemning every other "resistance" groups, setting up a seminary (without any real foundation)