I find it very interesting how the human sense of belonging to a group carries on as we keep, as a society, moving forward.
Arguing in favor of, or against it is not really what concerns me, but instead just observing how we change as we move closer and closer to the possibility of having to leave those old notions aside. I guess that's why it's common in sci-fi to have people born in other world have no sense of belonging to the Earth.
Probably a lot of the reasons for making it a big deal to return the flag in a US-launched vehicle has to do with PR, but still I can imagine that both engineers and astronauts will be very proud of making that happen nonetheless.