I think that this attitude is pretty common in a lot of slightly marginalised groups - getting so caught up in your own outsider status that you can't see the ways you are marginalising others. White feminists do it, for example, GLB people do it to transpeople.
That said, white cismale straight nerds are very privileged people overall - and not recognising this makes them the bullies that they so despised. They also take it a step further, by defining their own positive qualities as "masculine" and normalising their own experiences as universal (e.g. everyone who didn't grow up with a computer and is therefore comfortable with it is "stupid"). This article (http://restructure.wordpress.com/2010/06/28/male-geeks-reclaim-masculinity-at-the-expense-of-female-geeks/) is a good breakdown of this.
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That said, white cismale straight nerds are very privileged people overall - and not recognising this makes them the bullies that they so despised. They also take it a step further, by defining their own positive qualities as "masculine" and normalising their own experiences as universal (e.g. everyone who didn't grow up with a computer and is therefore comfortable with it is "stupid"). This article (http://restructure.wordpress.com/2010/06/28/male-geeks-reclaim-masculinity-at-the-expense-of-female-geeks/) is a good breakdown of this.