And if it doesn't remove a physical stain, then it must succeed in removing a spiritual stain, i.e. sin. The next sentence demonstrates that this is the correct understanding of the passage. And a good conscience is a conscience free from guilt. Therefore, water baptism is necessarily for the removal of sin and it's companion guilt. In other words, the baptism here contemplated will last until the end of time.
Water baptism is thus a permanent feature of the Christian system.
This infers that the subject of baptism can't be that hard to understand. It can't be a subject that demands years of study just to figure out the why, how and who of it. Therefore, the person who reject's any attitude or doctrine mentioned in this section, is guilty of spreading division. Such would be divisive and contentious behavior. God tells us to reject such.