Mike Philliber has given some helpful background on why the PCA sits strong when it comes to concerns regarding a slide leftward, especially when compared to other denominations.
He notes two things:
1) The 10 Commandments with explanation are a part of our constitution.
2) Our high view of the Bible when compared to other denominations. For example, one denomination considers the Word of God an “authoritative witness to Jesus Christ in the Church universal, and God’s Word to you.” This latter language gives plenty of wiggle room to sidestep certain aspects of the Scriptures that one finds inconvenient. The BCO language, on the other hand, rightly calls the Scriptures “the only infallible rule of faith and practice.”
You can read Philliber’s post HERE.