Since I'd at least like to think of myself as not one of those classic trolls who are unwilling to listen to others or admit that I'm sometimes wrong, I'll admit now to probably overreacting in this case, and being too quick to find slippery slopes where they might not really exist. I still think the other side could have done better at explaining in a logical way why that particular site needed to be purged, and to consider that I might possibly also have a point too, and not just be trolling to be disruptive, even if I might not have been right this time.
Giving a clear explanation that somebody was insidiously spamming that link and it needed to be blacklisted would have worked better with me than the seemingly vague and shifting rationales that people were actually giving in the debate, about it being an unreliable source (irrelevant when it came to removing links from discussion archives), it being a copyvio (maybe true, but the only proof they were showing was a boilerplate disclaimer in the site about not having copyright permission, but the identical text is used in many sites, some of which have valid fair use purpose), and it being spam (but even non-spammed links to it were being purged). It seemed like the explanations were being made up on an ad hoc basis so people could justify what their friend was doing.
My point, that making exceptions to the normal principle against editing others' comments in discussion was potentially dangerous, and was just the mindset that led to stuff like BADSITES, even if mistaken in this case, was never considered to be in any way a serious point rather than an irrelevant troll.