The book is pretty well derided as political propaganda masquerading as science. It's the same as the modern day "scientific" view that all Trump voters are mentally ill and Clinton voters are not.
For what it's worth, though...
>In his “Remarks on The Authoritarian Personality” (a text that was not included in the published 1950 work), Adorno laid out a series of objections that call into question the notion of an underlying personality structure; they suggest that under the modern conditions of the late-capitalist culture industry, the individual as a psychic unity is beginning to dissolve. This dissenting perspective deserves notice, especially in an age that has seen the reemergence of authoritarian politics in the United States.
By Adorno's reckoning, we have authoritarianism in both Trump and Clinton.[1]
[0] https://journals.sagepub.com/doi/abs/10.1177/016344371877214...
[1] "After first sketching Adorno’s conception of the “authoritarian personality,” with the help of Sándor Ferenczi’s concept of the “identification with the aggressor,” the article proceeds to examine the exchange of the letters between Adorno and Marcuse, illustrating Adorno’s changed orientation: that “fascism” or “authoritarianism” maybe either left or right. Finally, some conclusions are drawn about the authoritarian tendencies of the contemporary Left."