These lines suggest that he living is not enough, that one must have a purpose, and that honor might be one of those purposes. He suggests that a vulnerable prince marching to fight over a small amount of land puts him to shame, in a way, for not acting on restoring honor to his family, as his mother and father have been dishonored. This view seems to be a turning point for Hamlet, as it is in this point that he goes from being quite incredulous that an army would fight over such a small piece of land to realizing that he wasn't really living at all. He decides at the end of the act that any action not violent at this point is wasted. The view in question should be considered pivotal more than anything else, elucidating.
