There's absolutely nothing to be gained by arguing about word definitions, people treat definitions as axiomatic. People don't logically derive what a word means through etymology or historical usage, they define it as what they understand it to mean.
Telling someone that their definition of a word is wrong is like saying their preference for one colour over another is wrong. It's a personal view, accept it and move on.
Eventually, that makes communication impossible. If people are constantly reassigning different values to the same terms, you may have a conversation where each participant is actually discussing something different, and where the conclusions are therefore irrelevant.
To give you a current example, take REST. When a service says it has a REST API, it tells me absolutely nothing, since I don't know if they mean REST as in Roy Fielding's dissertation or REST as in "JSON instead of XML and some URL templates".
Their ability of communicating with me has been destroyed by people constantly reassigning different definitions to the term.
Hacker is a great one to pick on due to the name of this site. I'm in information security, and when I found a site called "Hacker News", I was expecting a bit more security research, not rockstar ninja bootstrapped VC-seeking programmers talking about Rails and the newest JS framework and how they founded a new startup with an MVP trying to disrupt a larger industry. That's not what hacker means to me. Writing code isn't hacking, it's writing code. The hackers I deal with on a daily basis are either my coworkers doing pentesting or the bad guys I'm paid to keep away from our networks. This is the only time I've complained about it, though.
Point being, words are often perverted by groups trying to describe their activities. This is how language works.