The Book of Mormon explains how and why it is worse to sin against the knowledge of God, for he who sins against the greater light shall receive the greater condemnation (DC 82:3). That is why the double wo is reserved for those in open rebellion, wo, wo unto him who knoweth that he rebelleth against God (Mosiah 3:12). On the other hand, there will be salvation for those who have sinned in ignorance, For behold…his blood atoneth for the sins of those…who have died not knowing the will of God concerning them, or who have ignorantly sinned (Mosiah 3:11).
Bruce R. McConkie
"Those saints who traverse the path of rebellion ordinarily do so by defying the will of God in lesser things, and then as their consciences and feelings become hardened, increasing rebellion becomes the established order. For a member of the Church to use tea, coffee, tobacco, or liquor is to rebel against the Lord and his law. Wilful absence from sacrament meeting is a type of rebellion; so likewise is wilful failure to pay an honest tithing.
"The degree of condemnation attending rebellion depends upon the nature of the defiance and the light enjoyed by the rebel. The Lord's anger is kindled against all the rebellious. (D. & C. 56:1; 63:2.) In due course they shall be pierced with much sorrow (D. & C. 1:3, 8) and cut off from the land of Zion. 'The rebellious are not of the blood of Ephraim.' (D. & C. 64:35-36.)
Those who have a perfect knowledge of the truth and who then come out in open rebellion will become sons of perdition. 'That which breaketh a law, and abideth not by law, but seeketh to become a law unto itself, and willeth to abide in sin, and altogether abideth in sin, cannot be sanctified by law, neither by mercy, justice, nor judgment. Therefore, they must remain filthy still.' (D. & C. 88:35.)" (Mormon Doctrine, p. 619)