"Generic" in this context has to do with replacing a specific topic with a larger, more general one that it perhaps has some connection to. The problem from an HN point of view is that it makes discussion less interesting and more flame-prone. The generic topics drown out the smaller ones the way a black hole will suck in everything that comes too close (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...).
That doesn't mean the larger topic isn't important. Most probably it is very important, far more than the more specific topic is. That's not what HN is optimizing for, though (see https://hn.algolia.com/?dateRange=all&page=0&prefix=true&sor...). Trying to stay focused on the specific rather than the generic, and especially the inflammatory generic, is a big part of keeping HN intact for its particular purpose. Otherwise it would quickly become purely a current affairs site, which it's not.
Here's another way of looking at it, in case helpful: we don't want anything predictable on HN. The rhetoric that people resort to when an issue like this comes up is fierce, repetitive, and predictable. That makes sense—if you're fighting for a cause you feel passionately about, repeating the same points as intensely as possible is what you do. But all of that is off topic on this site. There are plenty of other places to post that way.
Edit: I know how strong the temptation is to read something like this and think that the mods are taking the wrong position* on (in this case) abortion rights, and then get super mad about it. But I'm not saying anything about abortion rights (or California vs. Texas) in the slightest. I'm just trying to do the pedestrian moderation job I always do.
* https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
Political oppression is unfortunately highly predictable. This doesn't make it unworthy of discussion.