Edit: I looked up the justice department’s stance. From: https://www.justice.gov/atr/antitrust-laws-and-you
The Sherman Antitrust Act
This Act outlaws all contracts, combinations, and conspiracies that unreasonably restrain interstate and foreign trade. This includes agreements among competitors to fix prices, rig bids, and allocate customers, which are punishable as criminal felonies.
The Sherman Act also makes it a crime to monopolize any part of interstate commerce. An unlawful monopoly exists when one firm controls the market for a product or service, and it has obtained that market power, not because its product or service is superior to others, but by suppressing competition with anticompetitive conduct.
The Act, however, is not violated simply when one firm's vigorous competition and lower prices take sales from its less efficient competitors; in that case, competition is working properly.