This is not proof enough that Israel is guilty of war crimes. It's proof that the Israelis believe that many countries consider them guilty of war crimes, that Israelis fear that the UN has anti-Israel and/or anti-Semitic tendencies. They may be guilty of war crimes, but just because they wish to block Palestinian access to the ICC because they would be prosecuted does not mean that such future prosecution will be legitimate.
Report: Palestinian, 18, killed in clashes with IDF in West Bank (Haaretz)
from the article: In wake of Gaza flare-up, U.K. could support Palestinian bid at UN