It all started with the refusal to recognize antisemitism as a form of racism.
Here is the conclusion from Joel Fishman's article.
The 1965 debates in the Third Committee of the UN are a matter of great relevance to the present. A failed attempt of Israel and the US to have antisemitism defined as a type of racism resulted in two important setbacks: the failure of Israel to achieve a universally accepted definition of antisemitism with the force of international law and, a decade later, the UN acceptance of the libel “Zionism is racism.” From then on, it was almost impossible to raise the problem of antisemitism as a human rights issue. Others framed the reality of Israel, attributing to the Jewish State a completely specious and negative meaning. By setting the agenda of the international community, Israel’s enemies caused lasting harm in obstructing its claim to legal recourse in the matter of antisemitism. As a consequence, Israel must live with a disability and make do with a less than equal status in the community of nations.
One of the most valuable insights of this study is that there is a nexus between the defamation of Israel, as is the case with the “Zionism is racism” libel, and the need to ensure that antisemitism is defined as an internationally recognized human rights violation.