Recall that when Israel ended its occupation of Gaza, it did not impose a blockade. Indeed it left behind agricultural facilities [greenhouses] in the hope that the newly liberated Gaza Strip would become a peaceful and productive area. Instead Hamas seized control over Gaza and engaged in acts of warfare against Israel.
-Alan Dershowitz, with the necessary context
Given the Karine-A affair, the history of Gaza blockades in general, I find it hard to understand why some think that Israel - and the allies of peace - should be anything less than aggressive in pressuring the Hamas.