This was his final protest to a world that had ignored him, sometimes mocked him, always failed to acknowledge his superiority.
Robert Oswald, page 214 of “Lee, a Portrait of Lee Harvey Oswald”
And I believe that a large part of his motive had to do with the last part (underlined by me) of Robert’s statement. Robert also indicates that a pattern was apparent to him regarding LHO’s behavior. I will post Robert’s exact words about that pattern when I locate them in the above referenced book.
Michael Paine said something similar in his testimony. He said that Oswald was very bitter, very distrustful of people. But that Oswald placed himself as part of a larger class of people, that it wasn't just himself, that this mistreatment was "institutional", built into the capitalist system. Thus the embrace of the Marxist view of the world: oppressors and oppressed. So it was both personal
and political and not either/or.
Mr. PAINE: [Oswald] was extremely bitter and couldn't believe there was much good will in people. There was mostly evil, conniving, or else stupidity--was the description--that was his opinion or would be his description of most people. That's my description, and the best description I can give of him--to call him other psychological names--names of paranoia or paranoid or something like that.
Mr. LIEBELER - What made you pick that particular name?
Mr. PAINE - Well, that kind of suspicion of people expecting them to be consciously perpetrating evil or ill toward him or toward the oppressed people-workers-is perhaps a trait of paranoia.
Mr. LIEBELER - Do you think that he exhibited this trait?
Mr. PAINE - Yes; he did, but it didn't seem to be uncontrollable. He didn't generally take it--I would say he was paranoid if he always took it personally, but he always seemed to transfer it to, or put himself in the class of people who were oppressed, so that's the distinction why I wouldn't call him sick or wouldn't have then called him sick---before the assassination.
Mr. LIEBELER - Because he seemed to describe this feeling of his in institutional terms?
Mr. PAINE - That's right.
Mr. LIEBELER - And in terms of the social structure and the impact the world had on classes and groups of people?
Mr. PAINE - He was in the exploited class.
Mr. LIEBELER - Yes; there was no doubt about that--I mean, as far as his own mind was concerned--that's what he thought?
Mr. PAINE - Yes.