Well, people were going to that site to get the content, and now they are not (all) going there. Clearly the site has lost something, especially something that ties directly into their revenue. If one considers the content as a proxy for the lost revenue -- which is reasonable, since it's the content that attracts traffic -- one could say it's been stolen.
Of course, since it's not your work that is being mis-appropriated, you're free to look at it another way :-)
I would surmise that most readers of Hacker News either use an ad-blocker or don't click on ads often/ever. Viewed in this light, traffic to the site from here might even be considered a cost!
The advertiser usually doesn't care, since most ad blockers prevent the ad call, and their budget will be spent on another visitor. The ad blockers that render the ad off-canvas are bad for the advertiser, since they're getting charged for an ad that has no possibility of being seen.
Sites want as many unique visitors as possible because larger sites get more attention from advertisers, it permits better frequency capping, and enables better segmentation of audiences. Even though they get paid per impression, larger uniques tend to allow for higher CPMs.
Separately, it's worth considering that many writers are measured on metrics: uniques, minutes, shares, comments, etc. In some places, they might even get paid on such performance (I think Gawker did this). When content gets copied, the writer can be deprived of such credit.
> The ad blockers that render the ad off-canvas are bad for the advertiser, since they're getting charged for an ad that has no possibility of being seen.
I was wondering whether such ad-blockers exist. Searching for one and installing it now.
Of course, since it's not your work that is being mis-appropriated, you're free to look at it another way :-)