France hasn’t changed since Alfred Dreyfuss’ conviction. Antisemitism is ingrained in Europe, despite the multicultural illusions they cast.
It wasn’t French Monarchists and Ultramontaigne Catholics who did this.
Allow me to question your assumptions. Even the ultra-PC BBC article implies that the perps are Muslims. Muslims that, I might add, have been imported into France with the help of Jewish "anti-racist" lobbies.
This arson attach is an act of anti-Jewish hatred perpetrated by Muslims who hate France, don't want to be called French, and don't ever miss an opportunity to point it out (for instance by booing the French national anthem in a stadium, or desecrating churches, flags, etc).
I fail to see how this could be related to 19th-century anti-semitism, which never took the form of physical aggression.
Multi-culturalism, which you seem to hold as the answer to all racism problems, is often translated into "let's allow uncontrolled Muslim immigration and let's allow them to take over". As in England for instance. Again, this would produce exactly the attacks we see today.
I urge you to think hard about your assumptions. They don't jibe with reality.