What he did was a political analysis. So while he could provide citations to political scientists who said similar things that wouldn't make the true necessarily.
The "citation needed" only works if you want to assess the premises, so do you want a citation for racism being/having been more widespread or for Europe having had a antisemitism problem?
It's fine to not know everything, there are lots of thing I know nothing about.
When I don't know anything about a topic, I have found Wikipedia to become a great starting point to become less ignorant.
How France after having been a "laissez-faire" country (the fucking word is in French!) became the country it is today
https://fr.wikipedia.org/wiki/Programme_du_Conseil_national_...
How Clement Atlee transformed the UK
https://en.wikipedia.org/wiki/Clement_Attlee
https://en.wikipedia.org/wiki/Attlee_ministry
Why the US has for foreigners terribly obvious blind spots
https://en.wikipedia.org/wiki/American_civil_religion
Labor history of the United States
https://en.wikipedia.org/wiki/Labor_history_of_the_United_St...
History of antisemitism in Europe
https://en.wikipedia.org/wiki/History_of_antisemitism
History of racism in the United States of America
https://en.wikipedia.org/wiki/Racism_in_the_United_States
Thomas Jefferson and Sally Hemings
https://en.wikipedia.org/wiki/Sally_Hemings
Yes I'm pretty sure you are incomfortable with the topic at hand if you see absolutely no point in my "incoherent rambling"