"Since the blockade only prevented necessities from getting to the civilians in Gaza, but not weapons to Hamas, then the blockade can only be described as a deliberate attack on civilians, rather than a defensive measure,"

The blockade has been effective in reducing the flow of material to Gaza. Since it is the Gazans themselves that have decided what material to smuggle in ( using those tunnels from Egypt that Israel had no control over, and has now destroyed) the decision to bring in war material instead of that required for civilians ( food, medicine, etc) is entirely one by Gazans. If I choose to go out and buy a rocket to kill you with, it is hardly fair for me to then claim that you prevented me from buying food for my children with that money.