Jacob becomes very personal in his address. He is quite specific that the "wo" sections have been addressed to his audience. This re-emphasizes that each of the wo statements should be read not just in general, but as specific condemnations of actions being taken by the Nephites at this time.
Jacob has reproved his audience, and now tries to get them to understand the lesson. It is not just that these are hard words, but that they represent the necessity of a change in behavior. Jacob admonishes them to repent. The blessing part comes in that by so doing "they love the truth and are not shaken."