Corporations exist to increase shareholder (not management) wealth. If a takeover, hostile or otherwise, is in the best interest for the majority of shareholders, then any impediments to that are considered sub-optimal corporate governance practices.
What the curriculum is attempting to point out is that pre- and post-offer defenses exist and shows how they work. I think they generally try to stay agnostic about them, but there are a few cases (like staggared boards) that they simply feel are inconsistent with good corporate governance practices (with some exceptions like the one listed above).
A staggered board makes it harder for shareholders to ensure representation, but retains the knowledge base longer and makes hostile takeovers more difficult.