It demonstrates that it stifles copying. That may make it easier for the copier to innovate, but doesn’t dispute the main argument for having copyright protection: that, without the protection of copyright, the code wouldn’t have been written.

Sure, but given the timetable for changing the law, it still seems pretty reasonable to apply the same standard to Microsoft (and by extension Github) in the meantime

Yeah, that's a good argument to fully disprove this as a loss to society, and instead as a gain.

I don’t quite agree. Msft took a conservative approach to copyright to protect their own business.

Meanwhile open source software has had an immeasurable benefit to society. My computer, tv, phone, light bulb, etc all benefit from OSS—running various licenses, and only a subset using a copyleft like license.

That's the goal. To stifle using someone else's work.

Like, copyright laws are also stifling my innovative business creating BluRays of Disney films and selling them on Amazon.