The best statement of the philosophical case against antitrust is in philosopher Harry Binswanger’s essay, “Antitrust: ‘Free Competition’ at Gunpoint.” Binswanger draws a fundamental distinction between economic power and political power. Economic power, he notes, is simply the power to produce and trade, whereas political power is the power of the government and necessarily rests on the use of force or threat of force. Someone can earn a large market share, even, in rare cases, a 100% market share, without ever coercing anyone. That person creates power simply through his productivity and does not forcibly take anything away from anybody; therefore, he should not be persecuted.
I think that a lot of mass-market politics consists of trying to convince people that the market power of corporations is something to be feared, while the coercive power of government is not. The reality of public hoice is that government ends up using its coercive power mostly to advantage one producer’s interest over another. Consumers benefit more from the market, even when there is monopoly.