Because they will be suffer and possibly die.
Not resisting doesnt end well. That story has played out before.
No one is saying not to resist. However, if you are outnumbered 50 to 1, and in a country that will allow this attack to go on with out reprisal, then Jews generally suffer and die.
Europe is no longer safe and the fight is rigged. Time to leave. It would not have been the first time in history for Jews to run from a progrom.
Just one really rich guy could hire enough Yobs over there to address the problem on the sly. Once enough hell was raised, the problem would be so obvious people could no longer ignore it.
Ah but alas...no Right Wing Soros.
Except now there's a country out there who can get payback.