They often point to the damage that companies with large market shares—think Amazon, Wal-Mart, and Google—can do. These friends point out how these companies' large market presence allows them to squeeze out competitors, exploit employees, and hold customers captive.
Those points, of course, are debatable, but what really troubles me is that while these friends decry monopolies in commerce, they defend a huge monopoly: public schools. All the same criticisms should apply—but never seem to.
Recently, 60 Minutes ran an interesting piece on Google and why (according to interviewees) they are a monopoly. The segment's host stipulated that in 2017, 90% of all internet searches came through Google.