I think a lot of the disagreement between the left and the right boils down to disagreement about the appropriate form of the social welfare function. I think this applies not just to economic issues but also issues of gender and race.

While there quite likely is some degree of resolvable factual disagreement about the extent of certain inequities, and maybe-somewhat-resolvable disagreement about how those inequities might be lessened, there is also disagreement about how much those inequities should matter to us and affect our behavior, both political and personal. This is not the sort of disagreement I expect to see someone resolve in a blog post.

Now for a more blatantly left-wing argument: It is hard to get people to realize the extent and import of their privilege, to acknowledge that certain social inequities that are of minor significance when viewed from a privileged position are in fact deeply oppressive from the perspective of the marginalized. This is not the sort of thing that can be communicated by presenting scientific studies, because such studies may establish the existence of an inequity, but they do not fully convey the impact of that inequity on the lives and psyches of the population affected. The best way to acquire that sort of information is to listen to anecdotes from a number of marginalized people, a difficult thing to do on a website with demographics like LW has.