What that they don’t understand, maybe, is that being a real geek is a very bad thing for a lot of people. Geeks generally had a pretty rough time in school, socially, and rarely have much romantic success during the first portion (if not the entirety) of their lives. Many have crippling social or psychological problems that severely limit their ability to interact with others or work on any sort of team.
Sure, some geeks eventually make something of themselves with knowledge and passions, but many can never overcome their social problems enough to succeed in any field. Many, while they may like geeky things with associated careers (e.g. programming, math, science), aren’t actually very good at them. Many geeky people just don’t have any strong interests in the job-relevant areas — and the job market’s pretty small for experienced LARPers, fanfiction authors, and Trekkers. And many others are socially treated like geeks but don’t have the associated knowledge or passions — they just had some other social problem that caused them a lot of trouble in school, such as disorders, disfigurements, unattractiveness, or poverty.
For a clear non-geek to start saying they’re a geek for commerical benefit or trend appeal, it cheapens and minimizes the problems and pains that real geeks go through. It’s disrespectful at best.
Imagine the outrage if hip white people started wearing blackface and calling themselves the N-word because it was trendy. This isn’t anywhere near the same magnitude of offensiveness, of course. But it hits on the same sort of nerves: the “you don’t understand what we’ve gone through” sentiment, as if all of the trials and tribulations of a group of people with a rough past can be summarized by a few stereotypes and appropriated for its commercial or social value by people who never went through any of the same difficulties.
This sentiment is exacerbated by the continued problems and oppression of true geeks. Geeks haven’t gone away, and they haven’t become cool. People haven’t stopped being cruel to them, and they haven’t magically overcome their problems. Most of the people in that video would never give an actual geek the time of day.
A bunch of people incorrectly suggesting that they’ve suffered the same fate as a continually repressed group — repressed, sometimes, by the kind of people in this video — is offensive at best, and it degrades the reality of being a geek, the worst of which these people (with a small number of exceptions) will never experience or understand.