Outside of his silly comments about marginalised people, it does genuinely seem a little strange that maintainers of the project view themselves as some sort of punisher-style police force.
The context that's missing for a lot of the left leaning people hearing this is that much of the population of the US still sees police officers as heroes worthy of emulation. The thin blue line between order and chaos is a powerful image for a lot of people, and it doesn't necessarily have anything to do with being a punisher style police force.
The US is quite violent by developed world standards, and it borders Latin America, which is insanely violent even by poor world standards.
IIRC, of the 50 most violent cities in the world, 17 are in Mexico.
This means that a lot more people who have seen grisly things (beheadings by cartels etc.) are present in the US, and this raises the awareness about what could also happen in the absence of a police force.
Not really, but there's a long history of media that puts police on a pedestal in a fight against darkness.
The more cynical would call it propaganda, but I think there's more to it than that: it dates back to old westerns and draws from a rich history of hero literature. The police became a subject of that pre-existing tradition.
That’s sort of what the phrase has started to mean because of how it’s used by many American police officers. It has more reasonable historic meanings.
The "historic" meaning directly references a military regiment standing their ground against the enemy (see "thin red line"). This particular quote has always evinced a highly adversarial attitude.
So? The problem with the police using it for its historic meaning is that they are ostensibly not a military force but they act like one; using the phrase makes it almost explicit. Why is it bad if these open source maintainers use it, presuming they meant this “hold the battle line” meaning?
It probably wouldn't be bad (or at least as bad) if they used the original which isn't tied to the politics of policing. The “thin red line” inspired the “thin blue line”, but they are distinct sayings with different denotation and connotation.
Not that it is incorrect to say that the phrase is tied to policing, just that it is similarly not-incorrect to say it is not tied to policing. It is context-dependent. It’s not so obvious that this particular use of that phrase is at all related to police work.