Op is talking about people shaming and discriminating against a cultural niche, and then later assuming this niche and praising it for personal gain. Cultural appropriation in the way that you're referring to is copying a behavior from another culture which is blood and birth inherited. 

If a Caucasian person wears Asian dress for example, they lack the cultural context of geography, ancestory, and cultural practice that occurred within a particular societal upbringing. This is an entirely different argument to 'bullying someone for a cultural niche that is rightfully available to everyone and then later adopting that same niche with no regret or shame because it suddenly has a self serving purpose'. 

And by the way, what the fuck do you know about this persons' race?? Did they stipulate somewhere whether they are white or not? Did you just assume they can't be black because they subscribe to nerd/geek culture? That is, by definition, racist.