The current Gaza situation has context.
Gaza is ruled very strictly by Hamas, and nothing happens there that they do not want to happen. There could be no spontaneous mass demonstrations about anything.

Hamas is desperate to get its fighters across the border to kill Jews.
They have achieved that in the past by covertly cutting through and have even dug tunnels under it.

Israel has to consider that the mass demos are just a cover for more cross border Jew killing operations. They dare not allow a mass incursion into Israel.

Quite rightly, some Western nations are investigating the shootings to ensure they were justified.

Jim,
Israel has been carrying out massacres for decades

No it has not. If it had it would be a pariah among decent nations.
In fact it has good relations with every liberal democracy in the world.