Right, the submitted title ("Facebook's “free internet” programme is a cover for a land-grab") broke the HN guidelines by editorializing. That's bad. Submitters: please don't change titles unless they are misleading or linkbait (https://news.ycombinator.com/newsguidelines.html). If you want to present an argument, do so in the thread, on a level playing field with other users. On HN, submitting an article confers no special right to opine.
The subtitle ("Critics argue") would have been ok, but is less informative, and there's nothing wrong with the article's main headline, so we've put that in above.
Doesn't seem that editorialized. The "roadblock" is the feedback from critics, and the Economist's subhead is "Critics argue Mark Zuckerberg’s generosity is a cover for a land-grab".
It's not fair game. The site guidelines specifically demand that submitters not do this exact thing; instead, you're to use the article's original headline, unless it's misleading or linkbait.
People who submit stories don't own the stories on HN; stories are community property. Being the first to submit a URL does not give someone special privileges to reframe the story for everyone else.
In this case, the reframing that was done was overtly dishonest, implying as it does that The Economist endorses this point of view, which it clearly does not.
There is a significant difference between a headline that reads, "Facebook's “free internet” programme is a cover for a land-grab" and "Critics say Facebook's “free internet” programme is a cover for a land-grab". But both titles are sensational click-bait.
The subtitle ("Critics argue") would have been ok, but is less informative, and there's nothing wrong with the article's main headline, so we've put that in above.