The killing of the terrorist is not the issue. The issue is that Israel used forged passports of Ireland, United Kingdom, France and Germany in doing so. Thus endangering the citizens of those countries when they travel abroad on legitimate business, and in the case of the United Kingdom despite assurances that they would not do so. So if you were the United Kingdom what would you do?
Saudi-led coalition air strike kills around 30 Yemeni civilians (Reuters)
from the article: Germany, France also request Israeli answers on Dubai fake passports