Bias exists in every public forum

The argument

The marketplace of ideas depends on the open exchange of ideas, in which popularity is based on the value of the argument itself. This understanding fails to account for the bias that exists in all arenas. In political bodies, for example, party allegiance might determine how one chooses to vote. The concept is therefore too idealistic to be enacted in any society. We cannot say whether it works for doesn't for this reason: there is no precedent either way. Any argument on the subject is therefore pure conjecture.

Premises

Counter-arguments

The prominence of the marketplace in US legal defence shows this is not the case. At its core, the marketplace of ideas is a question of censorship. That it has successfully been invoked hundreds of times to challenge censorship, is proof that it can and does exist. And, that the existence of bias, is irrelevant to its operation.

Rejecting the premises

[Rejecting P1] The argument states the marketplace in its idealised form and then treats any departure from it as non-existence. A marketplace that operates imperfectly is a marketplace operating imperfectly — which is the sibling position that it does not work, not the stronger claim that it does not exist. [Rejecting P2] Legislatures are one arena, and among the least marketlike of those usually cited. The standard examples are courts, journals, universities and open publishing, and the counter-argument points to the concept's repeated invocation in US free-speech litigation as evidence that something is operating under the name. [Rejecting P3] "There is no precedent either way, so any argument is conjecture" is self-defeating. It is itself an argument on the subject, and if it were sound it would forbid the conclusion the argument goes on to draw.