I don't see how that follows. By "knowledge is a good unto itself" I mean that it is always better to know something than to be ignorant of something. Sure, some pieces of knowledge are more valuable than others, and we have a limited capacity for how much knowledge we can absorb and hold, but that doesn't contradict the premise, that having knowledge is a good thing. It just means we have to prioritize what knowledge to gain. Which is why, in that same sentence, I go on to explain why knowledge of current events is important.