"Because the Fundamental Beliefs document says that we believe in the key Protestant principle, the priesthood of all believers. "

The priesthood of all believers, simply means anyone can come to Christ without going through the church or the ceremonial law in the OT era.

It has nothing to do with negating forms and levels of government in the church community. If we followed your position, it would mean we can go directly to God the Father without going through Jesus Christ.

But we can pray for our friends, family, church, civil government or anything else we feel a necessity for and come to Christ in their behalf praying for grace in their behalf.

Thus the Reformers used this concept to negate the idea we must go through the church as the only means of grace. We can not ask God to forgive their sins, but we can ask for grace to bring them to Christ.