I feel like you changed the topic mid-debate, to something that one couldn't possibly disagree with.
I thought we were debating whether Jews should abandon the Democratic party.
I didn't think we were debating whether the far left has betrayed the Jews. On the later question, the answer is obvious, it is hell yes, and there can be no debate. If that was the topic, then we wasted our time because we already agree.
But I thought the topic of contention was whether Jews should abandon the Democratic party in light of this, which would involve exploring and debating the things that I tried to explore, namely
1) the connection, or lack thereof, between the Democratic party and the far left,
2) the record of the Democratic party politicians and mainstream supporters on Israel, and
3) whether the Republicans are any better.
Those were the three topics that I tried to explore.
And I made my case that
1) the far left has relatively little influence in mainstream Democratic party politics, and most of the far-leftist examples you cite do not seriously consider themselves part of the Democratic tent,
2) mainstream Democratic party politicians and people are supportive of Israel, and
3) part of the Republican 'base' has its own problems, with Ron Paul pulling 20% support.
So therefore, Jews have no reason to abandon the Democratic party.