That is easy, because Bernie is a Jew in name only. He does not practice judaism, he does not actively go to Temple and is not very religious. Now I have no problem with this but in the Jewish community Joe Lieberman is viewed Jewish, Bernie is not. This is from the NY Times, I am not sure you would understand it but any Jew would:
When Senator Bernie Sanders thanked supporters for his landslide victory in the New Hampshire Democratic primary, he wistfully reminisced about his upbringing as “the son of a Polish immigrant who came to this country speaking no English and having no money.”
While the crowd cheered, Rabbi Michael Paley of New York was among many Jews watching the speech who were taken aback. He said he was surprised that the Vermont senator had not explicitly described his father as a “Polish Jewish immigrant,” a significant distinction given Poland’s checkered history with its Jewish population.
“Nobody in Poland would have considered Bernie a Pole,” Rabbi Paley said.
When a black person like Hermin Cain or Condoleezza Rice show up republican, the black community labels them an uncle tom because they believe they are a sellout. Listen to XM left channel at 6:00 and you will hear the host trash any black republican no matter their upbringing or situation. Well the Jewish community has a similar stance on Bernie but it is more justified. Lieberman was a democrat that many Jews supported but most Jews see right through Sanders. That is why liberals love Bernie, he will eat his own and they will use him for that.
This is from another NY Newspaper:
The Bernie Sanders campaign is doing really well with hipsters who hate Israel. But there are two groups it just can't seem to crack. Black people and Jews.
The train didn't start going all the way off the rails until the campaign arrived in New York where it was embraced by the Hate Israel crowd and rejected by actual Jewish communities. After Bernie Sanders lied and accused Israel of killing 10,000 "innocent people", even his Jewish supporters headed for the exits.
And then the Bernie Sanders campaign decided to bring on board Simone Zimmerman, a BDS supporter and anti-Israel activist in If Not Now, a J Street front group harassing Jewish charities who help people in Israel, as its Jewish Outreach Director.
Finally I will leave you with this Good Knight Sweetheart:
“The great irony of the story is that Bernie Sanders does not have Jewish grandchildren — but Mr. Trump does. That perhaps explains why Bernie Sanders has not been greeted by the Jewish community quite the same way that, say, Joe Lieberman was when he ran for vice president in 2000,” added Sarna, noting that Sanders’ wife is not Jewish, and their children and grandchildren don’t seem to identify at all with Jewish heritage.