I'm a Jew-loving Jew. Anti-Semitism is never ok. Here's what is not anti-Semitism: Peaceful protest, criticism of the Israeli government, calling for an independent Palestine, demanding a ceasefire in Gaza, using the term apartheid to describe Israel, questioning Zionism.
Also not anti-Semitism: Condemnation of the serial war crimes and human rights violations in Gaza and the West Bank, demands for organizations to divest from states that commit war crimes and violate human rights, demands that the US stop providing weapons used in war crimes...
...and human rights violations. As offensive as phrases like "the river to the sea" may seem, they are no more offensive than the reality of an Israel seeking to exert their political control from "the river to the sea" and negate the legitimate claims of Palestinians.