I don't even know how wrong Bernie Sanders is, from his background perspective.
Today's J Street is yesterdays Zionists. The Zionists thought that as soon as we have our own country, be it Israel or Uruguay, people will stop hating us and we'll be a classic nation like all others. Today; they think as soon as we get Israel out of the way, modern society will accept us and anti semitism will stop.
As religious Jews, many of us believe that anti semitism is from hashem and is an inevitable part of golus. We won't be free from hatred until Mashiach comes.
However, from an atheist perspective (that ignores historical precedent), Mr Sanders and J Street may have a logically sound thought basis. I don't know if I would discredit him as an anti Semite, as much as disagree with the basis that brought him to his way of thinking.
(This difference in opinion comes up in many of the controversial threads on DDF, BTW. I'm not going to point out any examples, but it puts many arguments in fascinating perspective.)