Starship, if successful, will also change the economics of bringing down non-maneuverable satellites. I could see SpaceX cleaning up space junk as a public service.
Uplink/downlink bandwidth is licensed by the countries being uplinked/downlinked from/to, so that’s on them. China will no doubt not grant SpaceX a license.
Lots of space tech is “dual use”, e.x. GPS and many other communication satellites. As long as SpaceX isn’t hiding warheads on Starlink satellites or something I don’t see a problem.
How do you think they came up with that 50,000 satellite figure? Is that an underestimation? LEO is big but it will get harder as it gets saturated by starlink and especially if other companies try to create their own variations of the idea like amazon has expressed interest in.