Earlier quoted context omitted.
It doesn't matter whether a characteristic is innate or not; if it isn't relevant to the job, then nobody should be judged based on it. Even if you disregard that people can choose to change their gender or that politics can be inherited from the parents, gender and politics are interchangeable as far as social treatment is concerned. If you (dis)agree with the arguments of the memo in the gender/politics-swapped ver…
First and more important things: nobody is suggesting judging individuals by their gender. Damore's post was explicitly about not doing that. Of course an individual's suitability for a job should not be affected by anything irrelevant. However individual choices may be relevant: for example, you might not be suitable to work in the fitness industry if you're shy about showing your body. Hence distinguishing choices…
After reading this woman's opinion on Google's programs to increase their share of politically conservative workers, I realized that political bias, although indubitably present, might not fully explain the observed distribution of political alignments. To evaluate "affirmative action" efforts, the effect of bias would have to be quantified in relation to other phenomena incidentally correlating with political affiliation. However, I was disappointed that she didn't to that in her memo itself, arguing qualitatively instead of rigorously computing the expected distribution her suggested explanations would predict. The resulting number can easily make or break her case. Regardless of my opinion on her choice of presentation, I am appalled by the strong backlash from a group of vocal men within Google, some of which went so far as to threaten her with physical violence. Although the subject and manner of this discussion might not have been within Google's business interests, firing her for expressing her opinion (apparently in a forum where it was explicitly solicited) was definitely an unreasonably harsh response.
I think that gender and politics are plenty interchangeable in this case, provided you can suspend disbelief about Google actively trying to hire more conservative engineers and the media reaction surrounding this case.