It was brought up because they are receiving explicitly antisemitic content from the same people who loved and weaponized Tan's tweet.
A better question to ask yourself is why Jewish people seem to continually end up in this situation: on the receiving end of antisemitic abuse.
Political stuff pisses people off, but people who are pissed at Jew can always just trot out the antisemitic and dehumanizing statements... Such threatening comments have proved credible enough of the time to make the person on the receiving end really second guess about their safety.