well, given the topic, got to break this into two sections....
1. Concerning girl gamers. Never thought of games as a "boys only" thing, given my sisters played with me, my habit of trying to rope at least one of them into playing with me on whatever game I enjoyed at the time (goldeneye 64, slappers v. throwing knives fights were hilarious), and were skilled as I was most of the time. So when it comes to gender, no, the hobby isn't gender specific and any complaint about that is stupid. However; this goes to the next point.
2. The idea that the hobby is becoming more mainstream and the backlash against that. Now this I have more sympathy for. I've been gaming for a long time now, and while I am not so stupid to say I have "cred" or some bullshit, I do have a deep affection for the media and hobby and have had it for a long time. When I see someone identifying themselves as a "gamer" I often have to feel wary around them now though, be they male or female. This isn't so much an aspect of feeling better then people new to the hobby, but rather a distrust and frustration with how the term "gamer" itself has become less distinguishing and the people who try to opt into it who do not share the passion or dedication I do. I don't want to use the term "casuals" as that seems more to reflect a preference for a style of game, but it is more so... posers? Yes, I think that might be the right word. When I interact with someone like that, I suppose it would be similar to what a sports fan would feel trying to interact with someone who says they are as well, but don't understand half the rules of the sport, has a shallow understanding of teams and is more interested in being part of something larger then in the sport itself. It just feels fake, as if they are hanger's on and sad to say, many don't even express that much interest in trying to learn more. It is like a lack of passion for the hobby and instead merely a means for whatever social goal they have.
It is hard to word right, I think, why member of a group, a fandom or hobbyists would react negatively towards others trying to participate with them, but I myself often feel it when it comes down to the lack of passion or just the lack of shits given outside of how it helps their social goal. And it isn't about different preferences. I hate most FPS, but I can still hear the excitement and enjoyment in the voice of someone telling me about a wicked kill streak they pulled. I hate LoL, but I can still relate to the way someone will gush about a really good night. And for the most part, they seem to understand the same when I get into my own experiences in game. Some people though, and I don't exactly understand why except it being the "in" thing, seem to just call themselves a gamer but lack any sort of real passion behind it. And that in turn does effect the hobby. The rise of easier games, dumbed-down games, "broader appeal" game design...I know most of that stems from poor decisions in the industry, but those decisions are made because they see the swell of gamers, both enthusiastic and non, and start to try to cater to get new people, often at the expense of those that have been there for decades now because it is assumed that since they have stuck around so long, they are already safe bets they will for more.
So to wrap up, I never thought of this issue as much of a gender one, but one relating to popularity and how a sudden influx of posers can change the hobby I enjoy. I believe others pointed out how that affected genre of music over the years (and how in response to the influx, the aim of the music switched to the new demographic, narrowing the amount of people and money directed at what was enjoyed in the first place), and I am sure there are other things that exploded in popularity and as a result felt saturated by people who acted more like tourists then impassioned fans or hobbyist. I suppose given that a higher percentage of newer gamers ARE female, it leads to that mentality being misplaced on the gender, or being confused as gender specific. Makes things messy that way...