He broke labor and immigration laws and his behavior creates antisemitism. He can rot in jail.
I don't think so, I think he simply gives antisemites an opportunity to vent.
However that's irrelevant. He shouldn't be sentenced based on "violations" of labor, child labor, or immigration laws when he hasn't been convicted of such "violations". More accurately, hasn't been charged in the one case, acquitted in the other.
Whether you're right that he creates antisemitism, or I'm right he provides the Jewhaters an opportunity to vent, he doesn't get jail time for that. Only for the law he violated. And yes, the sentence is legal, though harsh. I doubt harshness is a function of the judges concern that he was creating antisemites.