Bali, Madrid, Israel
To kill is always bad, but to kill a terrorist or a terrorist leader, like Sheik Yassin, whose decisions caused and may cause the death of many innocent people, is right and necessary. The Israeli-style targeted killing of a terrorist by a precision rocket, reducing harm to by-standers to a minimum, seems to be the least bad way to do it. An alternative would be to try to arrest them which in most cases could cause much more collateral casualties, due to their deliberate hiding among civilians.
Few mourned the death of Saddam's two sons. Most people in the world would sigh with relief to hear Osama bin Laden was targeted and killed. There is absolutely no difference between Osama bin Laden and the head of Hamas.
Israel was right to kill that terrorist leader. Had the New York, Bali or Madrid terrorists or their leaders been targeted and killed before they engaged in those terrorist acts, every sound person would have applauded. Especially if they knew in advance what the terrorists were going to do. In Hamas' case we all knew.