More knowledgeable Christians should never mock or disdain weaker believers, nor should they become stumblingstones toward these brethren.
Sin demands atonement. Atonement puts God and man at one. When atonement is made man is cleansed and forgiven. In other words, things are made right.
In many ways, sin is simply sin. However, sins carry varying weights or repercussions. In fact, the Bible testifies that some sins are greater than others.
