Yeah, but the hard-earned wisdom the parent post is trying to impart is that if you think you want to avoid a subset of items, you're probably wrong.

In an explicitly enumerated category, blacklists and whitelists are logically equivalent and can be used interchangeably. In almost every other case blacklists are insufficient because new items can generally be created, either maliciously or just accidentally as the size of the category grows, which are not on the blacklist but which share whatever bad trait you were hoping to protect against.

I'm sure there are a few exceptions, but generally speaking any problem that can be solved with either a blacklist or a whitelist should use the whitelist, just to be safe. A problem that can't use a whitelist is probably not actually solvable by a blacklist either, and trying to use one is likely to fail in the long run.

That's just the definition of whitelist and blacklist?

My personal heuristic is to always favor the positive collection, which comes from databases where retrieving a set of data is much easier and more efficient than retrieving a set of data EXCEPT THESE. I always figured there was math to back this up.

That's literally just the definition of a whitelist and a blacklist. I think the comment you were replying to was making the point that blacklists generally work poorly in practice and should be reconsidered where at all possible.