Google had to pay billions for YouTube. The idea that Microsoft can go and take advantage of YouTube to their own business ends without contributing anything is legalizing parasitic behavior at best.
Then they shouldn't provide the API. Or they should charge for it. Or they should put limits on it that affect all providers equally. And why isn't that the case on iOS? Essentially we have Microsoft doing Google's job for them for free (and if it's not "Google's job" then why have they written an app for iOS while arguing that Microsoft can't release theirs because it wasn't written by Google?).