>How would you get over this mindset?
tl;dr: Ride the Tiger, brah
Fascism goes against modernity –More specifically, the Spirit of Modernity– one of the manny aspects of this Modern World is democracy, specifically the great deal of mental and spiritual consequences spawn from it, one of these –as I suppose the book covered– is the creation of an « Us-vs-Them » mentality. This division is the reason Fascism goes against democracy, or in other and less extreme cases it specifically seeks to end this division by changing the role of democracy in society –As, similar to capital or technology the problem is not the object itself, but its misuse–. However there is another consequence to democracy that is just as prevalent but more elusive. In a society which holds total participation in all sorts of decisions as a core aspect the idea that one must have an opinion on everything, that you must choose a side, that you are obligated to participate in the « Us-vs-Them » dichotomy is certain to arise. This causes all discussions to turn into combat, not only are people obligated to pick a side, sides are also expected to fight against one-another unless one wants to risks to appear ignorant, uninterested, unpatriotic, traitorous and all slander that could derive from it.
Buddhists hold Believes on a similar regard as material possessions, one must learn to be able to let go of our believes as easily as we should for material possessions. A practice I have seen among these cultures is for one to declare your believes only to have someone try to disprove it, and you are expected not to react. It is important for me to comment that this is not an expression of passiveness, that truth is impossible to acquire, nor teaching us that we are wrong in everything, but to take away the fear of being wrong, something which the simple thought of is enough to discourage manny. Once you have overcome this fear you will be at peace with your ideas, if you are right then good, but if you are wrong you will not be disturbed and change your views without hesitation. You can believe, you can defend your ideas, you can call others wrong, you can make assumptions based on those ideas, you can genocide entire races over those ideas, the truth is absolute and there are ideas that come closer to it than others, there is such a thing as right and wrong; but if you are ever convinced wrong then just leave it. Ideas maybe part of our identity, but just as no one would want to base their identity over bad habits we want to get rid of; you should have no problem in breaking away from wrong ideas. Now, Acting on your believes while recognizing that you are limited in your information-gathering means that the responsable thing to do is to take great care on what you learn.
This contrasts greatly with the stiff and educated leftist thought, who pride themselves over what they know and are capable of letting millions die, cut ties with one-another and ultimately fail over ideological purity; When you pride over your limited ideas –and due to our mundane existence they will always be limited– you are bound to make an enemy out of reality, and reality has no care for your believes, only herself. Back on the Old Board I said « Reality is where meme-Ideologies go to die » as a way to explain why manny people obsessed over politics only do theory and never try to put their ideas in practice, but now because of your question I found a new side to that phenomenon.
And when reading books do not approach them as a way to acquire knowledge, but to engage in a conversation with the author, it is a much less combatant approach so you should feel less the need to be defensive, you are not being taught something, you are being told the ideas of someone else. Of course, an unconscious need for validation may also make you insecure over your ideas matching the Autor's or just be on the side of people you hold in high-regard, but I do not want to expand on that because I do not want to sound accusatory.
I have said manny times that I find books a bit overrated, I think that I should clear a few things, specially now that it is relevant to an Anon's Question. Books are not a shortcut for experience, you should not seek information from books first, true wisdom comes from experience and self-introspection, because it is our experiences and ideas that make us; to analyze ourselves it is to analyze our ideas. And there is no time for introspection if you are constantly filling your mind with the noise from other people. I am not telling you not to listen others attentively, not even individuals you disagree with, but to be aware that these are the experiences of other people, and cannot make them part of your identity without making them yours first, simply agreeing is not enough, you must know how they all relate to your own experiences and fully integrate them, when brought up they should not be longer a « According to this autor, X happens » but a simple « X », these ideas should become such an obvious part of reality that no one could realistically claim ownership of them.