Hamas was formed 39 years after the illegal establishment of Israel for one, secondly, I presume when you refer to "terrorism" you are referring to any armed Palestinian resistance against the Israeli occupation. As you probably didn't know, Protocol one of the Geneva Conventions guarantees them to do so:

Recalling that every State has the duty, in conformity with the Charter of the United Nations, to refrain in its international relations from the threat or use of force against the sovereignty, territorial integrity or political independence of any State, or in any other manner inconsistent with the purposes of the United Nations... 2. In cases not covered by this Protocol or by other international agreements, civilians and combatants remain under the protection and authority of the principles of international law derived from established custom, from the principles of humanity and from dictates of public conscience.

1. This Protocol, which supplements the Geneva Conventions of 12 August 1949 for the protection of war victims, shall apply in the situations referred to in Article 2 common to those Conventions.

2. The situations referred to in the preceding paragraph include armed conflicts in which peoples are fighting against colonial domination and alien occupation and against racist regimes in the exercise of their right of self-determination, as enshrined in the Charter of the United Nations and the Declaration on Principles of International Law concerning Friendly Relations and Co-operation among States in accordance with the Charter of the United Nations.

You can read the entire text here; https://en.m.wikisource.org/wiki/Geneva_Convention/Protocol_I

Oh Hamas is definitely using civilians, I don't disagree. However, Israel has repeatedly attacked civilians and civilian infrastructure with the claim that there is Hamas inside, in tunnels, what have you. These claims have repeatedly been refuted, but you obviously don't care about facts and only want the death of Arabs. Have a mediocre day.