It’s the same way Islamophobia doesn’t become justified based on the actions of some Muslims.

Anyone who does do that is already a bigot, and would do the same to any other group, regardless of what they do.

A culture that normalizes hatred of Jews (or Israelis) as a group, will very quickly devolve into one where other minorities are hated as well. Because the youth, as gullible as they are, can still detect when a system of values is inconsistent.

A youth who thinks Israel should be genocided doesn’t care about genocide, so why hate Israel?

The hate in Europe is driven primarily by an influx of people who were hating Jews anyway, and who naively think that the hatred won’t backfire on them. Once you start promoting racism it comes for everyone.