How else do you fight terrorism?

Israel is facing an immense terrorist threat. Terrorism is not something that is easy to counter. There is often no central country that can be invaded to destroy the core of a terrorist group as there was in 2001 when the USA invaded Afghanistan. And even if there was there would be many lives killed and international condemnation. Assassination is one of very few ways to fight such terrorists. Killing them prevents them from engaging in attacks and disrupts their networks, while capturing them would be useful this is often not possible.

Capture would not be possible because the war against terrorism is if possible fought away from a the state's own home country in order to limit casualties and the chances of the terrorist to engage in his terrorist attack. Other countries object as much to kidnapping from their territory as they do murder on their soil. Unlike the USA who is able to persuade or buy other countries into supporting their conflicts this is not always possible for smaller countries such as Israel who do not have the influence or resources. Arab states are never going to help Israel murder or kidnap palestinians and other islamic terrorists on their soil even if they themselves are happy for those targeted to be disposed of.

Countries have never objected to kidnapping terror-suspects and torturing them unlawfully in extra-territorial prisons. 
 
Countries(via coalition forces) have sold terror-suspects they've captured to the U.S for this purpose. 
 
International Human rights Organizations, oppose these acts not countries; mind you.  
 
Point being, most terror suspects(ranging from Somalis, Filipinos,Yugoslavs,Arabs,British and even American[[http://www.washingtonpost.com/wp-dyn/content/article/2010/01/04/AR2010010400800.html]] in a recent case) have been to the U.S(and her allies) and were not killed nor captured there because murdering a thousand people to catch 5 suspects is impossible/impermissible/unacceptable on U.S soil; mainly because it is inhuman. 
 
Mossad has no right to take the U.S's 'bad behavior' as an excuse to take lives.