Even in the case that the target of drone strikes were threats, often times these attacks lead to a number of civilian casualties that, I think, could be in no way justified.
Or for example my fathers house being bombed in ww2 - they lived close to the biggest spitfire plant in the UK.
An attempt to give an analysis would be asking: what was the good reason to do it? I think that the answer to that question in the case of the drone strikes is not satisfactory.