Contemporary anthropology is...not very good. Latour's critiques are still quite strong and very difficult to overcome; perhaps anthropology
as a field is fundamentally flawed.
I haven't read Diamond, but I could understand, if you're a liberal academic and you see a text, almost like Nietzsche's Geneaology of Morals, that just says that the strong always conquer the weak because of totally contingent conditions, it will seem horrifying because, as a liberal, you genuinely believe in personal agency and social justice and all that fun stuff. But go back and actually read Marx, go and read all your favorite Frankfurt school thinkers: they will say, the conditions that we have been placed in are a real illusion of nature: even if the so-called nature of things is a construction, it is one where the reality of it is undeniable for us. Therefore, the goal of critique, even in that Marxian, Kantian sense, is to raise consciousness to shatter that real illusion precisely by illuminating this so-called "natural" process.
For Marx, revolution is a natural result of the development of Capitalism, but Capitalism also dissolved history, and temporality, so the naturality of revolution must be immanent in every moment of its development: its like Walter Benjamin said, we must bring about a real catastrophe, as opposed to the constant "accidents" of human suffering under the system that come about with almost mechanical regularity.
In any case, I don't remember Marx ever being either an academic, or particularly hard to read in most cases, even if a thorough familiarity with German Idealism is a great help to understanding him more deeply. Even Foucault was technically an academic, but only because he helped organize a nearly successful revolutionary movement that managed to extract the concession of an entire university (Paris VIII) out of the government which he then ran, and is still being run by his students and colleagues to this day.