I think we actually do start to see the author's opinion here. The author specifies in the first paragraph that the people who judge corporations with a moral lens are not just a subset of people, but rather a subset of a subset. "Many people complain about corporations"...but there are also those whose criticism goes further and who hold corporations morally to blame for many of the problems in Western society." thus, in the second paragraph, the "we" in "It is only by extension that we attribute the quality of morality to corporations, for corporations are not persons" cannot therefore be seen as a declaration of a belief or instinctual reaction of people to corporations generally, but of a belief of the sub-subset which that group's membership is defined by. Because the author declares this with "we", he/she is thus indicating membership of this sub-subset, which indicates the author's position.