So I understand that this is the kind of copy that is frequently used to sell clothes. "Thou art insufficient! Accept my wisdom and I shall lift thee from thy ignorance!" It's just like every crappy teen movie, make-over show and magazine cover.
It's also not appealing. Your vision of "nerd" seems to be nothing but "young white guys who don't work out much": who thinks of themselves that way? It is possible to be a fashion nerd, approaching the topic from a scientific, data-driven, rules-based or technology-incorporating point of view. An article about the history of pants got a bunch of upvotes a while back. MIT has clothes that strip pollution out of the air. That's nerdy fashion.
When talking to nerds, I wouldn't don't assume the audience will be sold by being told that there is something wrong with them that you can fix. Instead, be passionate and apply a nerdy lens to whatever that topic might be. Most of us are perfectly capable of doing the research to look good, and most of us don't bother. We don't need a savior; we might use some automation to lower the effort involved.
Thanks for your input. I enjoyed your thoughts on approaching things in a "fashion nerd" sort of way and was intrigued by the ideas of date-driven and scientific research to back up a point of view. However, I'm here to give simple fashion advice to guys who are willing to take it. They are perfectly capable of doing the research to look good; my hope is they'll find 140 Stitches to give it to them.