The blood bond was a clever way to explain not just the summer, but Hermione's behavior 6th year as well.
The idea that Hermione would feel betrayed by Harry setting her free from bondage and control was mindless drivel.
The idea that any of them would have insisted Harry return to durzkaban to be raped should be clear to all of them that they are all being compelled. Maybe they cannot see it in themselves, but they should in one another.
Letting the rapists live makes no sense. And yes, both adults are complicit in the act, and therefore need to die. That Harry sees Dudley is not a complete waste of flesh doesn't excuse his near decade of abuse, however he was 'following orders', just like a good nazi. It would be nice if he lived, scarred and filled with nightmares of them dying to death eaters, spending his remaining childhood years in a neglectful foster home would be true poetry.