Earlier quoted context omitted.
The kids could just be inclusive and switch to Telegram or WhatsApp or even Messenger. But the kids want to discriminate — humans, particularly Americans, thrive on excluding other people. the kids are just imitating the patterns they pick up from adults.
That's not how it works. These kids didn't create the stigma for the green bubble. Popular culture did, big-money TV, movie and music productions did, and teens are the most susceptible. Try finding a recent US-produced music video or hit movie/TV series that shows a green bubble (or Android for that matter, as it still has a higher market share).
Ultimately this is a larger societal problem of exclusion. America has taken it to its extreme, with racial segregation, redlining and the prison industrial complex. This iMessage nonsense is just a small and relatively benign symptom of the fundamental problem with America.
As a left-libertarian who believes in inclusion, I'm sure not going to encourage this with my own kids.