I've run into this position before on many things of unrelated matters and it never really agrees with me. I think mostly because redefining something does not inherently change what that thing is. 80% of the U.S. population may define Yoga as a bunch of twists and contortions, but people who know what yoga really is do not agree that those 80% are actually practicing Yoga. Likewise, if posting an unfortunate status update on someone's FB, that you found left in the logged in state at the library, suddenly became defined as "hacking" by 76% of the FB community, would you be inclined to agree with them?
Firstly, it's not a position; it's the fact of how communication works and how word usage evolves.
About liking it or not -- well, I don't like it, I care deeply about clarity of communication, and I despise how many debates on subjects like evolution, abortion, and all things political are derailed by (sometimes intentional) muddling of words' definitions.
So certainly, if you can convince everyone to re-adopt the original, more useful definition, then you have won and I salute you. Certainly you have the right to try -- sometimes it's very important to try and wrestle words back from the brink of uselessness.
But if you can't, then you are the odd one out. If everyone says "hacker" and means "someone who does stuff I don't like using computers", when you use the word with another meaning in mind, you are failing to communicate.
And the dictionaries will eventually start putting "archaic" after your definition.
If an article titled "How Hackers can use your credit card number" goes into details about what they mean by "hacker", examples of botnets and phishing, and mention that hacking in the criminal world can mean something different than what it means in the programming world, then I would have no problem with that.
This article was much more along those lines than the example you gave here. It often uses the term "yoga exercise" or "position", etc. and to state the specific action which caused an injury, or in the case of bikram yoga, to state a physical negative effect that it can have on the body.
In other words, it's what 80% of the population uses, and stated in such a way that the other 20% can tell exactly which of the many definitions of "yoga" the author means.
But then if real hackers came along and read that article, and then poised to point out that the "hackers" described in the article were not actually hacking but were rather engaging in an nonsensical tangent activity that could loosely be grouped within the technical field but not necessarily termed "hacking", we would then have to defend hacking by "redefining" it on the spot..
Not that I entirely disagree with you. I have no problem with observing a group performing such acts and pretending to define themselves within the collective for a group in which their activities really do not apply. I can certainly agree with saying "Fine, let them be." Until those activities begin to reflect badly upon the real collective, and then you must come out and explicitly distinguish between the real and the imaginative.
In your scenario (using someone's still-active account), I'll say it's ignorance from the author. But that's not the case here. My scenario (details about phishing attacks, mention that there are other uses for the word hacker) is much more comparable to the NYT article.
The author of the NYT article appears cognizant of the differences in different yoga forms, and of its history in the US and in India. This article uses proper usage of one of the many accepted meanings for "yoga", in a way that's understood by the readers and by domain experts.
Were real hackers to complain in my scenario, then to them I say "you've lost." They don't get to decide language, and real black-hat hackers embrace the term for themselves while many proficient white-hack hackers do not. People in the 1990s tried to introduce the term "cracker" as a substitute but that didn't take. The war is lost. Embrace (or accept) the white hat/black hat spectrum and get over it.
To yoga people who care about the precise term, just start saying the specific kind of yoga you mean. And don't call it "true" or "real" yoga.
