Rhetorical: Alma now emphasizes the positive aspects of his message. While there may be sin, there is also repentance, and the essential message of the atoning Messiah is precisely the ability to repent and to "take away the sins of the world." Very particularly, in the light of the sins of this particular congregation, Christ will also take away "the sins of every man who steadfastly believeth on his name."
Note that one of the phrases that Alma uses is "concerning that which is to come." This phrase refers to the coming of the atoning Messiah. This is also a particular contention with those who are not church members. In fact, it is this particular teaching that will become even more important in the next several years as the time of the Lord's first coming approaches.