"Collective punishment" is a misleading term when applied to international relations. In same way, raising of tariffs is a "collective punishment" of people involved with certain businesses (inside and outside the country) while reduction of tariffs is "collective punishment" of people involved with other businesses.
In international relations, the key term is "security". The government says that Israel security requires blockade of Gaza. It can be disputed. But blindly rejecting any kind of blockade is simply misleading language used by people who don't understand basics of politics and/or try to manipulate public opinion.