He says exactly that in his comment. There is no law stopping them from doing it.
In my haste, I read that as "there is nothing stopping them from being pro-consumer, so there is no reason to assume that the judgements favour the businesses" for some reason.
One contract along those lines that I saw basically goes like this: each party picks its own arbitrator (presumably biased toward that party, whatever). Then those two arbitrators together select a third arbitrator, who will actually arbitrate the dispute.
Of course that's not what binding arbitration clauses look like, at all.
Are the arbiters really hired by the company?
As for the hiring part - the business pays most of the arbitration fees, but the consumer is on the hook for a nominal amount plus any attorney fees and potentially extra costs like expert testimony.
There are obvious incentives for the arbitrators to favour the people paying them - individuals are not going to be doing a lot of business with them, companies are.