Hey Diane, not all Lefties are "anti-Israel."
Nor is such a stance limited to those on the left.
And as for this question:
"Why do I never hear any of you denounce it? Why do you not forcefully declare that you will have nothing to do with a movement that in any way uses the vocabulary of anti-Semitism, or in any way advances its ideology?"
This is very reminiscent of the time Jerry Falwell was on a talk show opposite the leader of a Muslim-American group saying "why haven't any of you denounced 9/11?" To which the guy responded "we have repeatedly." To which Falwell responded "but I haven't seen these denouncements," proving once and for all that if a tree falls in the woods, and Jerry Falwell isn't there to hear it, he's still a corrupt bigoted idiot.
Point being - put your big wide brush away and get a smaller one out if you wish to have a serious debate with people.