The reason that people are annoyed is because the title of the article is misleading. Yes, this guy may be a "hacker" in the sense of the word that we all like to use (he's a programmer).
The issue is that the article is titled "Why you don't steal from a hacker". This is not actually an appropriate name for the article, because it's not the writer's status as a hacker that leads to the final result. It is the writer's position as an application user that leads to the final result. In that sense, this article be should called, "Why you don't steal from someone that knows how to use an application to track their stolen laptop". Hence, by replacing the the "application user" with "hacker" you are diluting the meaning of hacker that everyone here loves to use. I'm not trying to be critical, just explaining why people are stating this and that they are attempting to express a consistent stance. You may associate this type of activity with a hacker, but understandably, it is not what you'd come up with when you attempted to define a hacker.
I think the headline implies that a hacker/security professional is more likely to have something like prey installed than, say, someone like my non-technical mom.
I think that's also a very reasonable point of view. However, at the same time, I its also reasonable to say that there is a group that could include people we would consider non-hackers that use this type of application (e.g., those with any sensitive/private information on their computers). Maybe they wouldn't use the exact same application, but something to track their laptop may be of use. Then again, maybe those people can afford a system with a built in tracking devise that can't easily be removed (requires more than just wiping the system). Meanwhile, hackers are left to add a "hack" to their computer that can do the same thing.
Honestly, I see your point, and both sides. I've just met a few people that have a similar service installed onto their phones, and I certainly would not call them hackers. Similarly, if someone told me they had this installed on their computer, I wouldn't think, "Oh, cool! S/he's a hacker!" On the other hand, if I saw someone starting "Learn Python the Hard Way" I _would_ think, "Oh shit, s/he's becoming a hacker!". Anyway, I don't really care too much. You do make a good point though. In general, a hacker might be more likely to aggressively try to track you down :)
The issue is that the article is titled "Why you don't steal from a hacker". This is not actually an appropriate name for the article, because it's not the writer's status as a hacker that leads to the final result. It is the writer's position as an application user that leads to the final result. In that sense, this article be should called, "Why you don't steal from someone that knows how to use an application to track their stolen laptop". Hence, by replacing the the "application user" with "hacker" you are diluting the meaning of hacker that everyone here loves to use. I'm not trying to be critical, just explaining why people are stating this and that they are attempting to express a consistent stance. You may associate this type of activity with a hacker, but understandably, it is not what you'd come up with when you attempted to define a hacker.