"Mein Kampf" is a good example of well written propaganda.
Like any good propaganda, it starts from true facts, so the first part of the book describes real problems of the society at that time (most of which are again problems of the present society).
The real problems would capture the attention of the readers, who were heavily affected by them in their own real lives.
Also like any good propaganda, from the true premises the book transitions to conclusions that do not result from the premises, but are falsely claimed to do so, and then solutions to the false conclusions are presented as if they will solve the problem described by the true premises (i.e. life is bad => the reason why it is bad is because there exist Jews => eliminate them and life will become good).
The same propaganda scheme from "Mein Kampf" is frequently applied today, but usually the Jews are replaced by China or by legal immigrants or by illegal immigrants or by people supporting another political party, always failing to identify the real culprits for the "life is bad" premises.
I do not agree that any propaganda books must be banned based on the condescending idea that humans are stupid, but I believe that it should be mandatory that any propaganda book should be accompanied by a well-written rebuttal, which should explain where the book in lying and why its conclusions are wrong, for the benefit of those less experienced, who might not notice these facts themselves.
I understand your discomfort with these books, and I actually agree that they deserve to be banned, but banning is not what we should do.
Its ultra important for historical/social and linguistic education.
I read it when I was 14, and I'm from Poland.
It is AWFUL and PAINFUL to read due to the horrible styling - which amuses me to this day. :) That's why no need to ban it hehehe
Nowadays books are for intellectuals, not for the masses... That's why I would be ok for any modern teenager to read anything 18+ or anti-whatever books :) It's net positive no matter of content IMO.
I guess when it comes to Freedom of Speech, you fall into the latter category.