So what if DHH said in a Twitter comment that he liked breasts and that we should give in to "our animal instincts". Is that sexist? Was he speaking for the whole RoR community?

Here are my assertions: (i) Just because some idiot created slides with naked women on them for his conference presentation, you cannot argue that the software community is sexist or male privileged or whatever. (ii) Prof. Spertus' comment includes reverse bias: When she writes "[I was] wondering if he had either not expected any women to be there or had discounted the importance of directing his remarks to the women in the audience", she's automatically assuming that those slides would be offensive to women only, i.e. all the men in the audience are brainless cavemen that drool over the oversize pictures on the screen.