The Israeli reaction has nothing to do with massacres of Christians in Syria. The enmity between Alawites and Christians on the one hand and Sunni Muslims in Syria goes back to the effects of French influence during the Ottoman empire, when Christians and Alawites benefitted "disproportionately" as the Muslims saw it from economic changes introduced by trade with the French, and the later French imperial presence after WWI where the French used Christians and Alawites as local allies.
From what I've read, the current massacres were prompted by Alawite militia attacking forces of one of the Sunni groups allied to the new government.
The Germans killed the Jews because the Nazis saw them as murderous parasites, when in fact, there was probably no group more loyal to the German state than German Jews, who even suffered proportionately more deaths in WWI than the overall German population.
The accusation of being murderous parasites, however, fits the Palestinians and Alawites in Syria far better. The Christians are simply grain caught between the millstones.
The Israelis teamed with the Islamic “head choppers” to take down the Assad regime. This was none of Israel’s business, and certainly working with Islamic assassins in not good. In any event, Israel celebrated the Head Choppers victory and then engaged in land stealing from Syria and has stood idly by while the people it colluded with kill Christians in big numbers, something that was not done under Assad.
Israel is the root cause of most of the violence in the Middle East.