The Boycott, Divest and Sanction movement against Israel is often seen as progressive — so it’s astounding to see its supporters turn to racism.

The latest target: Chloé Simone Valdary, an African-American undergraduate at the University of New Orleans and founder of the Allies of Israel Association.

Valdary recently wrote an article criticizing the Jewish Museum’s decision to invite Judith Butler, a University of California, Berkeley professor and outspoken BDS supporter to speak — an invitation Butler at first accepted, then declined.

BDS supporters’ response to Valdary was vile. Activist Zaid Jilani tweeted, “Non-jew [Chloé Valdary] smears famous Jewish academic as ally of Hitler,” then mocked her outspoken stand against anti-Semitism. (Jilani, by the way, was ousted from a liberal think tank last year for use of what his boss called “terrible anti-Semitic language.”)

Then there was Max Blumenthal, a former writer for the pro-Hezbollah Al Akhbar newspaper. (The Nation found Blumenthal’s recent book notable for its “equation of Israel with Nazis.”) He tweeted that Valdary is “beyond sickening” and “irrationally hateful” — and a “non-Jew” who represents “the future of Zionism.”

And Richard Silverstein of Tikun Olam, a blog focused on “exposing the excesses of the Israeli national-security state,” posted on his Facebook page, with a link to her piece: “They finally did it: found a Negro Zionist: Uncle Tom is dancin’ for joy!”

The attacks from his allies are offensive enough, but Silverstein’s racial slurs are beyond the pale. And his river of hate continued to flow, as he called this young African-American woman a “house slave” and said the “Israel Lobby is her Master.” His racist intent with such loaded language could hardly be more clear.

For many in the African-American community, the phrase “Uncle Tom” is as bad as, if not worse than, the N-word. The pejorative has historically been used against African-Americans seen as subservient to oppressive whites.

Few words could be more hurtful, especially from a Caucasian man publicly castigating a young African-American woman.

I’ve seen this too many times before: a supposed “progressive” stepping on the backs of African-Americans, then walking away as if the pain he’s inflicted is different from that caused by any other racist. Why should such hate speech go unchallenged, just because it’s cloaked as criticism of Israel?

As a civil-rights activist and leader in the African-American community, I’m exceptionally disturbed to discover that the response to this attack on Valdary has been subdued, almost nonexistent.

Just as Jews stood with African-Americans during the fight for civil rights in the 1960s, so too must we as leaders of the Black community stand together today with Chloé Simone Valdary, on the one hand, and the Jewish community, on the other hand.

Don’t dismiss this incident as a one-off. It represents a deeply troubling trend in an anti-Israel movement that goes way beyond honest criticism of Israeli policy to dehumanize and vilify Israel, Israelis and anyone who supports the Jewish state.

They do so not only through calls to boycott a liberal democracy, but also by dropping any pretense of decency, fairness or humanity.

To these haters, all the basic rules of liberal society — rejection of hate speech, commitment to academic freedom, rooting out racism, the absolute commitment to human dignity — go out the window when the subject is Israel.

For years some have warned that opponents of Israel are indulging in a new form of anti-Semitism. The vilification of Israel may not always be carried out by non-Jews or directed at Jews, but the dynamic is remarkably similar to the old version. The caricatures, the obviously twisted double standards and the hatred that drives it are all the same.

Canadian Prime Minister Stephen Harper put it eloquently before the Knesset in January. Calling the anti-Israel hatred “sickening,” he added that “This is the face of the new anti-Semitism. It targets the Jewish people by targeting Israel and attempts to make the old bigotry acceptable for a new generation.”

We who have visited Israel know the truth first hand. The country isn’t perfect (whose is?), but it strives for peaceful coexistence with its neighbors. Israel is the Middle East’s lone functioning democracy and by leaps and bounds the region’s leader in respecting human and civil rights.

Israel welcomes Arabs as citizens contributing to its democracy and legislative process, its military institutions,and universities, sitting in its parliament and in high judicial posts. It’s also the only nation in history to bring tens of thousands of Africans (Ethiopian Jews) out of Africa to be citizens, not slaves.

Valdary’s writings eloquently make the substantive argument for Israel. The comments by Silverstein and his allies show that there is still hate, racism and ignorance in this country that must be confronted.

So while Chloé Simone Valdary continues to fight for Israel, let all good people denounce Silverstein’s racism and stand with her. This is doubly true for liberal Americans, who have so long stood for rooting out hatred, discrimination and bigotry. They should make clear that they believe in these things just as strongly when it comes to the subject of Israel.

Anthony Hardy Williams is the Democratic whip in the Pennsylvania state Senate. His father, Hardy Williams, worked alongside Martin Luther King Jr. and broke the color barrier at Penn State.