assalamu alaykum
As for Hamas, they are incharge of the Muslims in Gaza. Allah forgive them and all the Muslims. Allah give the Muslims in Gaza and all Palestine , in other parts of the world, such as Chechnya, Kashmir, Azerbaijan, Bosnia, China, Burma, Iraq, Indonesia strength.
Suicide bombings are haram in Islam, however, I think people need to go to Palestine before making judgements. I have been and one thing I remember is the utter hatred and racism of the Israeli Jews and that is totally opposite to the Kindness and beauty of the Palestinian Muslims.
It is duty for all Muslims to unite and give strength to the Ummah and never let another brother or sister down. As for those who have the power to make a difference, whether they are incharge of Muslims, whether they are businessmen or have any ability to do something, if they fail to take action, then they will be held to account on Yawm al Qiyamah.
assalamu alaykum