Concrete, steel, building materials can be used to reinforce bunkers, rocket bases and smuggling tunnels. The more "harmless" items such as butter and so forth is used by the terrorist group Hamas to trade on the black market for more millitary worthy items.
LOL...
Hamas imports weapons from Egypt. How many arms dealers do you know that would trade a truck load of butter for a rocket launcher?
A blockade is designed to not only keep millitary items out but to also make it hard on the citizens that put this terrorist group in power. This is the case with MANY blockades conducted by MANY countries. You make it hard on the citizens and they finally get sick of it and kick the terrorist out of power.
Not only is collective punishment a war crime under the Geneva convention but it downright morally unfair to deny aid and economic development to 1.5 million people for the actions of their government.
I've heard this excuse over and over for years and the only thing I see the blockade doing is making Hamas even more powerful.