Also, it's irrelevant whether you agree with me or not, because it's not going to change the fact that we have a free and open system where anyone can modify the code as they see fit and users are free to run whatever code they want.
Well, that's the end of your argument, isn't it.
Because several attempts have already been made to release code that, okay, doesn't steal the project, but destroys the network the project runs on, in favour of a re-designed network. And the XT attempt included code to prevent future hard forks that weren't Hearn approved. And no-one bought the premise that either of those protocol redesigns offered something valuable, and so the fork didn't happen.
As for your more desperate point ("pursue a new, incompatible chain and create an altcoin"), pleeeeeeeeeeeeeeeeease.
We both know it's a soft fork. We both know that means the chain is compatible, and certainly not new, it's the same chain. We both know that this means old clients can use old features, but not new ones. Hmmmmm, it's almost as if every other soft fork that's been activated has those properties, and Segwit is no different.
So, your argument is fine, as long as you agree that Bitcoin is now on something like it's 6th or 7th incompatible altcoin reiteration, lol. Which means your point is invalid, as soft-forking changes have happened many times already without incident.