The majority of European antisémites have zero problem with the existence of Israel "out there". They are more than happy to see the Jews leave Europe for the middle east. American antisémites are fantasizing that Israel will be the site of the Second Coming of Christ who will then turn all the Jews into Christians.
This observation alone should tell you everything about why it is stupid and wrong to use attitudes towards Israel as proxy measures for attitudes towards Jews. When the antisémites pass your metric with flying colours whereas Jewish anti-Zionists fail it, your metric is just shit, simple as that.