He was an external research associate at the Vidal Sassoon Center for the Study of Antisemitism (SICSA) at the Hebrew University of Jerusalem from 2004 to 2015.
Currently, he is a member of the German Council on Foreign Relations DGAP and of the advisory board of UANI (United Against Nuclear Iran).
His essays and articles have been translated into sixteen languages and published inter alia in The New Republic, The Wall Street Journal, The Israel Journal of Foreign Affairs, The Weekly Standard, Telos, Policy Review, The Jerusalem Post, Der Standard, Spiegel Online, Die Welt, Die Zeit and Internationale Politik.
[2] In 2005, he discovered antisemitic tracts at the Iranian stands at the Frankfurt Book Fair, an incident he wrote about in the Wall Street Journal.
The book was criticized by Gilbert Achcar as "a fantasy-based narrative pasted together out of secondary sources and thirdhand reports; it aims to demonstrate that there is a direct line of descent from Amin al-Husseini and Hassan al-Banna through Gamal Abdel-Nasser to Osama bin Laden.
According to this picture, the rebellion was brought about by the machinations of the mufti who just followed his lust for power and his anti-Semitic leanings and who already at that time colluded with the Nazis.
The real background of the revolt, the Palestinians' apprehension at enhanced Jewish immigration, accelerated Zionist upbuilding and the possible loss of their homeland, is absent from this picture.
In 2010 he became a guest commentator on Germany's main public radio station, Deutschlandradio Kultur, and addressed the "Second Conference of the Interparliamentary Coalition on Combating Antisemitism" in Ottawa, Canada.
In 2012, he spoke on behalf of the Henry Jackson Society to Britain's House of Commons on the 70th anniversary of the Wannsee Conference, and at the Konrad Adenauer Foundation in Brussels on the current meaning of the Auschwitz day of remembrance.
Wie der islamische Antisemitismus entstand" (Nazis and the Middle East: How Islamic antisemitism came into being) was published in 2019.
However Hennig writes the book an overdue contribution to the awareness of a topic which plays too little a role in scientific and general public discourse.