Once upon a time there were anti-semites who wanted to promote their ideas in public and get away with it, but open anti-semitism was frowned on.
They needed some way to deny being anti-semites, while verbally attacking Jews.
One option they might consider is to say, "We don't hate Jews, we just hate Israel." This would let them say all the nasty stuff they want about the Jewish state, and the Jews there, while pretending not to be anti-semites.
This would get them a larger number of TV appearances, newspaper articles, etc, than if they introduced themselves as anti-semites.
No organization or cooperation or central planning is needed for this to become commonplace. Once a couple people try it out, and get publicity, then others will see its effectiveness and can copy the technique.
Today this technique is a daily occurrence. It's used to repeat traditional anti-semitic propaganda with only slight changes.
For example, "Jews murder Gentiles for pleasure or ritual" becomes "Israelis murder Palestinians for no reason" (except that, apparently, they wanted to).
"Jews kill babies" becomes "Israel is a child-killer state."
"Jews cheat at business and steal" becomes "Israeli settlers, especially right-wing orthodox Jews, steal land and water."
"Jews (via conspiracy) orchestrate major world events" becomes "the influential Jewish lobby is behind X"
Blaming Jewish victims for provoking their murderers is a staple of traditional anti-semitism, and of the "anti-Israel" rhetoric today, which finds ways to blame the Jews that Hamas kills.
So when someone says "I'm not anti-semitic, I'm just saying there are legitimate criticisms of Israel," and then says exactly the same things he would say if he was anti-semitic, he is either anti-semitic, willfully closing his eyes to anti-semitism, or extremely naive or ignorant.
For an german as I am it is a minefield to speak about Israel without being considered Anti-Semitic.
I help this problem by reminding my talking partner that paelstinians are semitic too, that there is on the other hand no semitic race, but only families of language.
Remains the problem of Israel critic as anti-judaism. I have no problem with jewish religion and comunity life, but with the government of Israel for the methods they use to fight terrorism.
The politic against gaza right now reminds me of some terrorists hiding in a supermarket full of innocent people, and the police blowing it away.
Tobias Mueller Kortkamp
Difference between a state and individuals living under its jurisdiction
There is a huge distinction between the set of people who self-identify as Jews and the state of Israel. Just as one can be critical of the U.S.A. (say, if one believes that torture is wrong) without being against the people who inhabit America, so one can be critical of Israel (even to the extent of saying things that an "anti-semetic person" would say) without being anti-semitic.
To elaborate on my previous comment, I am an anarchast. As such, I am highly critical of Israel, as I am of most states. I condemn their actions in the clearest terms, no doubt echoing the sentiments of various anti-semites. On the other hand, though I am not religious myself, Judaism is my favorite theistic religion, and I do not consider myself anti-semetic.