When defenders of Israel have to equate any criticism of Israel as being anti-semitism in origin. They are admitting they can't defend Israel on the facts.
To his question
'Why does the Left only protest when Muslims killed by Jews?'
This isn't a left / right issue. This constant framing of things is something the right does as some kind of presentation that there's always two distinct alternatives. Plenty on the right are against Israels atrocities against the Palestinians. Further to this, Gillard, Shorten ect are all massive Israel supporters. Trying to frame things as left / right is a way of telling people on your side, which tends to always be the right saying this, that they don't need to listen to the other side. They know people can be convinced on the facts about Israel to not support to persecution and oppression of the Palestinians. The last thing supporters of Israel want is for people to truly be informed. They can't win on the facts. Hence label everyone as anti-Semitic to try and claim there's no legitimacy so people remain ignorant to the facts.
It's simply a tactic to stone wall debate as it's a debate Israel can not win on the facts and realities.
Further to Bolts point. Syria killing Syria is not a conflict we are supporting.. well not directly. It's a different context when it's Western Colonialists committing crimes against those they colonise and a regional instability.
People protest in Australia because countries like Australia enable and allow the Israeli actions. Once Israel loses international support it will have to stop its land grab and try and make some sort of peace.
If we protest Syria or Isis, what Australian policy change can help those people suffering?