"Brother J received from Elder K a false theory of sanctification, which is outside of the third angel's message, and wherever received destroys the love for the message. I was shown that Elder K was upon dangerous ground. He is not in union with the third angel. He once enjoyed the blessing of God, but does not now, for he has not prized and cherished the light of truth which has shone upon his pathway. He has brought along with him a theory of Methodist sanctification, and presents that in front, making it of the highest importance. And the sacred truths applicable to this time are by him made of little consequence. He has followed his own light, and been growing darker and darker, and going further and further from the truth, until it has but little influence upon him. Satan has controlled his mind, and he has done great injury to the cause of truth in northern Wisconsin. 1T 334.1"
"But there were false prophets also among the people, even as there shall be false teachers among you, who privily shall bring in damnable heresies, even denying the Lord that bought them, and bring upon themselves swift destruction."
The EGW quote warns against a false teacher bringing in a false theory, which aligns with the warning in 2 Peter 2:1 about false teachers bringing in damnable heresies.
"But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed."
The EGW quote warns against a 'false theory' and someone preaching something outside the accepted message, which is similar to the warning in Galatians 1:8 against preaching a different gospel.