Because its actually Hezbollah that murdered them by (a) initiating the fighting and (b) by fighting surrounded by "civilians". Israel's choice was its civilians or Hezbollah and that meant Lebanese "civilians". Of course, some of these were actual civilians. That is regrettable and even deplorable but its also tough. Israel had no choice, except that choice it made to fight with one arm tied behind its back - as in not unleashing all it had.
Security cabinet meeting convened to assess security situation in Israel's south ends (Haaretz)
from the article: Israel to UN: Hezbollah has tripled its land-to-sea missile arsenal