People have been protesting against Facebook's policies almost since it was created (real-name only, no nudity even in classical art pieces, ...). That didn't change a thing. Facebook kept in-line with its policies, people stayed, and network effects only cemented the monopoly.

Github is extremely close to having a monopoly, leaving is the only way to prevent it from happening. If it becomes one, it has no incentives to listen to a few protests.