I don't think parent is calling the entire blog spam, there is definitely good, original content on the blog itself. But this particular article is what's called "blogspam":

> A blog where the author paraphrases or copies from the original article/webpage in an attempt to increase his or her own traffic. This becomes a waste of the reader's time forcing them to click through the blog to get to the actual article. Often submitted to sites like Digg or Reddit.

https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...

The relevant part is "to incrase his or her own traffic".

Bruce Schneier is one of the most famous cryptography researchers. I doubt he needs more traffic. Intent matters, and when he reposts and summarises a Guardian article, this is probably done for the benefit of readers who already follow his blog.

IMHO not including the words "The Guardian" in his TL;DR is what makes it spammy