The BDS movement, which aims to “boycott, divest and sanction” Israel and those who do business there, has long walked a line between opposing Israel’s treatment of Palestinians and fomenting hatred of Jews and Jewish culture. But now one of its affiliates has plunged headlong into outright antisemitic bigotry, conspiracy theories and implicit invitations to violence.Late Tuesday, Boston’s arm of the loosely organized movement urged its followers , as it had several times before, to explore an interactive “Mapping Project,” which it said would show “how imperialism, racism, militarism & Zionism are systemically connected in our communities.”It does none of...