There is real danger of misunderstanding and anachronism when taking a look at the terminology of "segregation" as used in the context of Belloc's book on the Jewish People. This particular term most certainly did NOT connote for Belloc anything close to what it certainly *came* to connote for Americans and then the Western world (namely, something forced upon a group as the result of diabolical prejudices).
As this book is availablen ON-LINE to read (not kept hidden away by thought police -- which is always a terribly scary idea, please let it be kept in mind), it is available for ALL to study and thus to render a rationally well-based yet well-roundedly empathetic judgment as to the character of both book and author (being careful to avoid holding Belloc to a standard only fully appreciated later on, a standard that no one -- Jew or Gentile -- held anyone to at the time of Belloc's writing).
Personally, after my having read this book, I'd be happy to attest to two things: (1) Belloc was no anti-Semite, nor was he an anti-Zionist. His whole book, in some sense, can be seen as motivated by the very opposite sympathies, tendencies evincing a genuine human compassion for his Jewish brethren. (And, in any event, certainly *not* by some malevolent desire to see them removed from his line of sight!)
(2) Belloc's wording of his views (as well as, though less radically, the views themselves) would surely have been altered by dint of what took place thereafter -- especially, of course, the great Atrocity itself. Apropos of his own proferred *solutions*, while he would certainly have a good deal of very *different* ideas to contribute regarding how to go about fixing the contemporary counterparts to problems he had dealt with (if any), I certainly could not begin to guess as to what his proffered remedies might be!
If anything, however, Belloc -- IMO -- deserves honorable mention for his prescience in recognizing the dangers posed by those socio-political forces which continued unabashedly afoot against the Jewish people, forces in play in large part due to the courage so honorably evinced by many Jewish people in being unwilling to relinquish any of that sacred patrimony (tradousis) so carefully handed down since the fall of the Second Temple.
More to the point, there can be little question that the same forces that Belloc in large measure points out were the very forces that effectively contributed to the great horror, as if arising from Hell itself, that just was the Nazi Holocaust.
Now, as with any *knowledgeable* Catholic of the time, Belloc was *FAR* from being sympathetic to such forces. Notwithstanding any intramural controversies regarding the prudence or lack thereof for continued emphasis on an obligation of the *polis/civitas* to acknowledge a particular religion as uniquely "true" or "official" (a judgment, to my understanding, long ago adopted, as is its right, by the contemporary State of Israel), the moral unanimity of Catholic intelligentia at the turn of the 20th century had ALREADY embraced the essential mindset -- carried over from Thomism to the Enlightenment era -- apropos of the *grave need for recognition of the rights of man* (viz., of the fundamental ontological basis of *any and all reasonable claims* as would impose a GRAVE MORAL DUTY OF TOLERANCE -- both upon one's fellow man and upon one's government -- as concerns those things most intimately associated with the personhood of the given individual -- his/her life, his/her conscience, etc.).
This felt need on the part of Catholic intellectuals of the time was, if anything, *especially* heightened when it came to the very People to whom Catholics were utterly convinced God -- given His awesomely perspicuous "particularity" -- was so lavish and extravagant in providing manifold signs of their "Chosenhood" -- and even when such lavishness might have otherwise been at the risk of scandalizing the "nations" (and then for AT LEAST two and a half millennia) and/or having the latter call into question the truly universal character of the God of Abraham, Isaac and Jacob, one and unique Creator of the entirety of the Heavens and the Earth.