Hamas was elected with 76 of the 132 available seats in the Palestinian parliament. That is a 57.5% majority.
I understand why Hamas was elected. The Palestinians feel that they are owed their lands, and want to fight for it. So they elected radical elements in their country to lead them to prosperity. The same reason any political group comes to power. The issue is that Hamas is on many major nation's list for being a terrorist organization. From Wikipedia:
The United States lists Hamas as a "Foreign Terrorist Organization".[34] Canada officially describes Hamas as a "a radical Sunni Muslim terrorist organization."[224][225] The European Union lists Hamas among the entities against which it applies restrictions in order to combat terrorism.[37] Israel's Ministry of Foreign Affairs states that "Hamas maintains a terrorist infrastructure in Gaza and the West Bank, and acts to carry out terrorist attacks in the territories and Israel."[226] Japan stated in 2005 that it had frozen the assets of "terrorist organizations, including... Hamas."[227]
That would lead me to believe that Hamas isn't as rosy as your trying to paint it. They are the duly elected leaders of the Palestinian people, and should be treated as such. And if they commit acts of war, they should be treated with proper response.
Now, for the OP - I do think that it's prudent that a full investigation is led into any atrocities committed. Soldiers should be punished if they violated Geneva convention rules, or did anything outside the lines of the proper conduct of war. I just wonder if Hamas would do the same for their irregular army.
Back from the dead, I'm afraid.







