I'm sure those anti semitic posts come from left wing trolls. Thats the point. When jews vote for Kerry they are voting with people that hate them. The only anti-Isreal posts you see on conservative sites are those posted by liberals.
Wishful thinking I'm afraid. There are legitimate issues regarding the far lefts association with antisemitic and terrorist interests, I don't think kerry.com banning antisemites is much of an issue.