I’m Jewish (I’m even a mod in our Jewish community here on lemmy.world) and I am very sensitive to antisemitism, but there is also a lot of ignorance which you can call a form of soft bigotry if you like, but it does not rise to something I would consider antisemitism.
It could very well be that this was a case of a bunch of ignorant people.
Someone else suggested (based on the article itself) that it may have been coincidental and the protest just happened to be in the vicinity of the musical.
Or they were a bunch of antisemites.
I don’t feel like I have enough information to judge.