Here is a very general point that applies to the first part of 34 -- "injustice is not an evil in itself" -- that's hugely important on it's own, but it is really nothing more than application of the physics that there are no eternal rules or supernatural gods dictating what is "good" and "evil" in itself. Ultimately Nature has only given us pleasure and pain by which to judge what is desirable and what is not, so neither "injustice" or anything else is "evil" in itself, with the closest to "evil in itself" being only pain, which is always undesirable, and yet sometimes we even choose that in order to gain greater pleasure or avoid worse pain.
So the main point -- injustice is not evil in itself - stands alone, with the rest of the explanation of why injustice is "evil" or "undesirable" being to point out that the undesirability comes from other factors besides supernatural prohibition or violation of any kind of absolute rules.
As for how it relates to 32, 32 is supporting the point that what we consider to be "just" and "unjust can be judged only in terms of whether there are breaches of agreement, because there are no supernatural or absolute obligations which can be breached.
One more point -- That's why I think that the 12 Fundamentals of Nature should always be included in discussion of the 40 Doctrines. What we are discussing here derives directly from the Epicurean physics, which confirms the nature of the universe as natural, and eliminates the possibility of supernatural or universally absolute law. If you try to divorce the discussion of justice from the nature of the universe as if they were separable, you tear away the support and foundation of the conclusion, and leave it dangling and appearing to be arbitrary.