Once somebody - or some event - pulls it into the light, we can at least become aware, but even then it's often easier to go with the status quo - the sexist or ableist language, laughing along with the jokes - than to take a stand.

My personal blind spot is girlyness - I loathe pink and skirts and makeup and almost anything that is traditionally coded as 'female' - it took me a very long time to acknowledge that a) some women (and some not-so-obviously-gendered-people) LIKE them without being brainwashed by the patriarchy, and b) just because someone likes traditionally-coded-as-girly clothes and pastimes doesn't mean they haven't got a sharp mind and that I should dismiss them as fluff heads. High heels or pink do not make a person stupid.