Thank you, all.
There is significant disagreement on this issue among sincere believers, as you well know. I'm not sure it's fair to assert that if someone searches the Scriptures enough or is diligently taught by the church he will necessarily embrace paedo-Baptism. Credo-Baptists could make the same claim conversely. Some accept it and some don't. Some accept it with minimum diligence and reflection in order to fit in. I don't think the ones who fail to embrace it are in sin any more than those who do embrace it are in sin.
Don't you think the principle articulated in Rom. 14:23, "But the man who has doubts is condemned if he eats, because his eating is not from faith; and everything that does not come from faith is sin" has application here? If someone consents to have his infant baptized against his conscience, is he not sinning?

I think the reference in BCO 12-5 is referring to someone who believes the doctrine of infant Baptism and neglects to see to it that it is applied to his children. To that person, it would be sinful. There is no "neglect" on the part of credo-Baptistic adherent in the PCA. The term "refusal" and not "neglect" would be the more appropriate term if that were the case. That seems to be the only way to reconcile these two parts of the BCO.