Call it the pangs of intimacy. As Israeli Prime Minister Benjamin Netanyahu cultivates relationships with Central European heads of state, he has had some uncomfortable moments. A recent spat shows how quarrels over Judaism’s history in the region can complicate cooperation.

During a foreign-policy conference in Warsaw two weeks ago, an Israeli reporter asked Mr. Netanyahu to comment on the controversial “Polish death camps” bill. Signed into law in February 2018, the legislation made it a crime to claim “contrary to the facts”...