In what way can this law possibly be considered good or have any redeeming value?
The leftists opposed it because it hurts Muslims. If it hurt only Jews or Christians the leftists would be happy about it. But in this case it hurts Jews as well, as you acknowledged. In France they ban it even in public, not just in public jobs as Quebec now did.
Would you be happy if the government banned circumcision or religiously slaughtered meat, since after all that would hurt Muslims and leftists would support it as being child cruelty and animal cruelty? Just because the leftists oppose something doesn’t be definition make it good.
The French Quebecois are particularly nasty antisemites and have a history of Jew hatred.