It has been determined by Islamic law that the blood and property of people of Dar Al-Harb (non Muslims) is not protected. Because they fight against and are hostile towards the Muslims, they annulled the protection of his blood and his property.
Yusuf al-Qaradawi(God) gives the weak a weapon for self-defense that the strong, despite his military and nuclear arsenals, can do nothing against. There are clerics who condemn this and even say that these are suicide operations that are not allowed in Islam.
Yusuf al-QaradawiIbn Ata' Allah said: "God may open up for you the gates of obedience, but without opening up for you the gates of acceptance. On the other hand, He may Allow you to fall into disobedience which happens to lead you to the right path. DISOBEDIENCE that teaches you HUMILITY is better than PIETY that fills you with VANITY and ARROGANCE.
Yusuf al-Qaradawi