And you're right not seeing them that way!
While I'm sure there are now good-faith bootcamps that have the goal of improving the career options of people who may otherwise never get those, the first time I saw the programming/sysadmin bootcamp concept implemented was around 2002, where a company was recruiting kids still in high school to train them for their openings.
They did that because there were not enough skilled IT workers back then. Right, what that really meant is, they did that because there were not enough skilled IT workers they could afford back then. Someone did the math and estimated that for some openings, it would be more profitable to train first-time-job-seekers (in a lot of cases, not-yet-job-seekers) than to offer a better deal. They're still in business so I guess it worked!
I really don't buy the "some people just can't help being an asshole so having a rule against assholes is exclusionary." The most controversial CoC is by far the Contributor Covenant and rules are be kind and empathetic, show others respect, don't insult or demean others, don't be creepy or sexually harass others, don't doxx people, and behave like adults at work. Like the bar is so low.
The history of the developer circles is that we've been a bit rough with the language. (mount, finger, touch, zip, etc are perfectly acceptable things for linux commmands.. theres even a joke about it). Unsavory jokes in mailing list/code bases, etc. However, we've come upon a bunch of people who take the aggressively negative view on the words and interactions used and have taken it upon themselves to rename things and force changes. (Master/main, master/slave, whitelist/blacklist, [theres a whole list of these "undesirable" language things] etc ).
On top of that the CoC has implemented toxic positivity rules on projects. Implementers overlook the fact that they have been used as a weapon to be put in the project it's self. (There have been examples of racial, and gender based discrimination in the enforcement of the rules)
All of this brings in people who do not contribute in a UX, DX, engineering, management sort of way. Even when these things are abused/enforced poorly it still has a significant silencing effect and distancing effect from those who would be a positive contributor but is reluctant to participate.
But to address the level of statements: I see SJ as one part of it, not the only or major part.
> enthusiastic nerds
Maybe it's the spaces I'm in but I'm not seeing that these days. I'm not hearing about personal projects people have made anymore. I'm not seeing a lot of enthusiastic young presenters at conferences etc. I'm just seeing younger people trying to stand out in the rat race and they aren't similar to when I was growing up. (I.e. lan parties, identifying as nerdy people and grouping together, etc).
The last young person I recall being like that was a guy who did a presentation on using Joycons at Scaladays 2017? This was a kid that did have experience in the us first robotics group. But f me.. a high schooler pretty good at Scala.. that's awesome!
But I just don't see e.g. for-profit bootcamps with their simplified curriculum as any kind of social justice project.