In every movement there are going to be extremists and people with prejudice.

However, you don't need to be antisemitic to be anti-Zionist. There are pretty much infinite reasons to denounce Israel, and the state seems to be making more every day.

If I, or anyone else, wanted to make a poignant argument against Israel we could simple gesture to the pile of crimes against humanity the state has committed. We wouldn't need to resort to antisemitism.