Ah yes. The invisible magic hand of free market that solves all problems. Except it doesn't. See Uber expanding its service where for a small fee you can avoid dealing with people from undesirable social class. Not exactly the same thing, but still the idea of free market promoting immoral solutions rather than eliminating them.

> At what size can/should the government step in a force companies to do things?

At a size when the society starts depending on your service for daily functioning. When it becomes essential. For example in my country it's an issue that you can't have a business without a bank account but sometimes banks just... refuse to make an account for you and your company won't function.