Playing Devil's Advocate here a little bit but why is it, factually, wrong? Favouring a group of people based on a characteristic (here faith) at the expense of others who do not have that characteristic is as much racism as using a characteristic to degrade someone who has it whilst promoting those who don't. The objectivity of racism is the same. The subjectivity of its application is what is being challenged here, no?
My understanding of Zionism is that a self-defined group of people are claiming they are different to other humans (i.e. a separate race) and as such should be allowed their own homeland, in a place where their faith has historic ties, and where their race is legally protected at the expense of others (a jewish state for jews).
What other 'race' or, in this case, religion, is entitled to this?
It will lead to more anti-semitism but that is because it is an excuse for anti-semitism rather than creating it. That already exists and this is just another avenue for that foulness to be aired.
All people have a right to be safe and protected, and this is where current (and historic society) has failed those of the jewish religion but no country has a right to exist and no community has the right to be promoted or protected at the expense of another. What is the difference between Tommy 10 names and the Faragist spiel of 'England for the English' and the Zionist 'Israel for the Jews'?
I do agree that the Green Party have screwed up here but this is also not Polanski or the leaders fault. This was a proposal from the floor, as per their party constitution, that got the votes to become policy and has not been supported by Polanski or the MPs. But if you have party rules that allow the members to set policy rather than the executive, then this is what can happen.