Mostly I agree with Scalzi, and Penny Arcade said it well: there is no gate, you're not the gatekeeper. And yet, there's something there worth parsing to get to. Here's Maddox's blistering rant on You're not a nerd, geeks aren't sexy and you don't "fucking love" science.
Again, as a general strategy it's often helpful to get used to thinking of things in terms of fuzzy sets and points on a spectrum, in this case ranging from very geeky/nerdy, to medium, to mainstream, to- well, the opposite of geeky/nerdy is stupid, mindless, lazy, sloppy.
If some trendroid wants to wear an Avengers shirt, fine. More money for a good franchise, Joss Whedon can do more cool stuff. What pisses some geeks off is outsiders appropriating the surface appearance without understanding the underlying depth, and that's not a dilemma unique to geekdom, it's a common, near-universal thing in all fields. This isn't a gender thing, or a geek thing, there are posers, posers everywhere.
What I empathize with is the hardcore obsessive's disdain and contempt for the dilettante. But not for the beginner! If you love what I love, I'll give you my books, babble on incessantly, subsidize your descent into addiction to the thing we love, you are my brother. What's frustrating is the dabblers who will forever just skate on the surface and never go any deeper.
PS, as with most things, self-selection is weak evidence; if you call yourself a geek, well, talk is cheap. When other people call you a geek, then that's the real nomination.