After graduating high school he worked for the Holland America Line at the SS Rotterdam.
He later became critic of the "leftist elite", especially the leaders of the Labour Party, as Roel in 't Veld and Bram Peper.
In 1981 he obtained his doctorate with the thesis entitled "International Networks of Banks and Industry" under supervision of Rob Mokken.
He has published many scientific publications in the field of anti-immigration parties, ethnic organizations and the economic and political elites.
Fennema also intervened frequently in the public debate with contributions on the opinion pages of national newspapers.
With John Rhijnsburger he wrote a biography of Hans Max Hirschfeld (Man van het grote geld, 2007).