Sez who? ;-)
Seriously: Every member of a hospital has to be well before the hospital can practice medicine effectively? Where do you find that all the Christians at the time of the council of Jerusalem were acting in such a way that those in the council were right to think of themselves as inspired by the Holy Spirit?
Did God judge Israel through Samson? Were Jeremiah and Isaiah ANd their religious communities "Operating in such a way as to be fully inspired"? Isn't this works righteousness in the final analysis?
I don't see that this notion has its basis in Scripture. To judge by what the Bible tells us happened in the early Church there was disagreement and misunderstanding of God's will regarding Gentiles, and yet God spoke through the Council, and did so so clearly that the Council claimed that what was said "Seemed good to the Holy Spirit."
7And when there had been much disputing, Peter rose up, and said unto them, Men and brethren, ye know how that a good while ago God made choice among us, that the Gentiles by my mouth should hear the word of the gospel, and believe.
8And God, which knoweth the hearts, bare them witness, giving them the Holy Ghost, even as he did unto us;
9And put no difference between us and them, purifying their hearts by faith.
10Now therefore why tempt ye God, to put a yoke upon the neck of the disciples, which neither our fathers nor we were able to bear?
11But we believe that through the grace of the LORD Jesus Christ we shall be saved, even as they.
12Then all the multitude kept silence, and gave audience to Barnabas and Paul, declaring what miracles and wonders God had wrought among the Gentiles by them.
13And after they had held their peace, James answered, saying, Men and brethren, hearken unto me:
14Simeon hath declared how God at the first did visit the Gentiles, to take out of them a people for his name.
15And to this agree the words of the prophets; as it is written,
16After this I will return, and will build again the tabernacle of David, which is fallen down; and I will build again the ruins thereof, and I will set it up:
17That the residue of men might seek after the Lord, and all the Gentiles, upon whom my name is called, saith the Lord, who doeth all these things.
18Known unto God are all his works from the beginning of the world.
19Wherefore my sentence is, that we trouble not them, which from among the Gentiles are turned to God:
20But that we write unto them, that they abstain from pollutions of idols, and from fornication, and from things strangled, and from blood.
21For Moses of old time hath in every city them that preach him, being read in the synagogues every sabbath day.
22Then pleased it the apostles and elders with the whole church, to send chosen men of their own company to Antioch with Paul and Barnabas; namely, Judas surnamed Barsabas and Silas, chief men among the brethren:
23And they wrote letters by them after this manner; The apostles and elders and brethren send greeting unto the brethren which are of the Gentiles in Antioch and Syria and Cilicia.
24Forasmuch as we have heard, that certain which went out from us have troubled you with words, subverting your souls, saying, Ye must be circumcised, and keep the law: to whom we gave no such commandment:
25It seemed good unto us, being assembled with one accord, to send chosen men unto you with our beloved Barnabas and Paul,
26Men that have hazarded their lives for the name of our Lord Jesus Christ.
27We have sent therefore Judas and Silas, who shall also tell you the same things by mouth.
28For it seemed good to the Holy Ghost, and to us, to lay upon you no greater burden than these necessary things;
29That ye abstain from meats offered to idols, and from blood, and from things strangled, and from fornication: from which if ye keep yourselves, ye shall do well. Fare ye well.
30So when they were dismissed, they came to Antioch: and when they had gathered the multitude together, they delivered the epistle:
31Which when they had read, they rejoiced for the consolation.
It pleased the council gathered there and it pleased the Holy Spirit after they sought for answers according to the scriptures (vv. 15-16 where the prophet Amos is quoted). It seems that after a time of disputing, there arose unity among the brethren. Disputing gave way to accord (one of the key characteristics of the early church—see earlier chapters in Acts). This unity is what pleased the Holy Spirit (and not the disputing).
Ephesians 4:2-6
With all lowliness and meekness, with longsuffering, forbearing one another in love; Endeavouring to keep the unity of the Spirit in the bond of peace. There is one body, and one Spirit, even as ye are called in one hope of your calling; One Lord, one faith, one baptism, One God and Father of all, who is above all, and through all, and in you all.
For, what else can be pleasing to the Holy Spirit except true, Christian unity. Or is Christ divided?