Back then, Israel was generally supported by the Left, except for the hardcore Communists who took their directions from the Soviet Union and therefore backed various Islamic "liberation movements." Jews were identified as heroes because the Holocaust was perpetrated against them by Hitler, whom the Left characterized as a rightist. The foundation of Israel was seen as a kind of victory over Hitler.
Now, Israel is hated by the left, even though perhaps the majority of Israelis are still leftists. How this came about is complicated. But it's not as if Hollywood used to be conservative and now are liberal. They were always liberal. But there was a time when it was considered correct for liberals to be patriotic.
That changed with Vietnam.
Maybe that is what people mean when they say that the definition of liberal has changed.