Children Of God By Faith?

"For you are all sons of God through faith in Christ Jesus." (Gal. 3: 26 nkjv)

When I was a young Hardshell minister this verse caused me (other Hardshells too) lots of problems. This verse seemed to teach, prima facie, that faith was the means or condition for becoming the children or sons of God. I used to ask other PBs about their views on the text. Most would say it means "you are all manifestly the children of God through faith in Christ Jesus." That used to bother me. Now, it still bothers me but in a different way. It bothers me now that Hardshells can be so stubborn in their refusal to accept what is plainly stated in scripture. It bothers me when such teachers of the word take such liberties with the word of God! Who gave them the right to add the word "manifestly" to the text? Does not adding that word change the whole meaning of the text? I used to hear them give the same explanation to John 1: 12-13. They would say that those who received Christ were given "power to manifestly become children of God." 

This is not the way to "handle" the word of God. It is dishonest. It is adding to the word of God and God pronounces severe punishment on those who do so. (See the final words of the book of Revelation). I will not do it. The text says that people are sons of God by faith in Christ. Why can't our Hardshell brothers not just accept the plain word of God? 

Elder John Clark, editor of Zion's Advocate (1854 - 1880), often referred to our text in his battle with the Hardshells who began to deny means and advocate against preaching to lost sinners. The first Hardshells had no problem telling men that faith in Christ was necessary in order to be labeled "sons of God."

They are sons of God by rebirth, but rebirth follows faith in our text. Would any of our anti means Hardshell brothers want to come here and defend their view in light of the above text?