Caplan’s analysis of reality may be correct (you have to pick your fights wisely, and high-status people will win more of their fights), but his prescription is completely asinine.
First, I don’t think that high status (i.e. professional) people are particularly meek. However, I do think that they may be more careful about how and when they assert themselves. If you want to get ahead, pick your fights carefully (i.e. don’t get caught up in your emotions) and choose strategies that will minimize the disturbance caused by your fight (and the potential loss of reputation). I’ve met people from working class backgrounds who extoll the virtues of pride-driven and loud self-assertion (as opposed to strategic and subtle self assertion), and explicitly describe this as a “working class” ethic (as opposed to a professional class ethic).
More generally, his prescription illustrates a common conservative fallacy: “if one person did it, then anyone can do it; and if anyone can do it, then everyone can do it”. Neither of those statements are true, yet conservatives regularly conflate these three issues (one, any, all).
In fact, his observation that high-status people will win more fights is a perfect illustration of rankism, and why the status quo will necessarily produce a dominance hierarchy that has little to do with merit.
p.s. by “conflict” and “fights” I am including things as mundane as negotiating over wages, where there is still a conflict of interest even though both sides will likely walk away happy at the end.