Them thinking it doesn't make it true. I'm certainly not bashing blind culture, deaf culture or any other culture here, but they are, in fact, "broken". They have organs that don't work as designed. Doesn't make them lesser people, doesn't mean they aren't as happy, fulfilled, mean, frustrated, joyful, etc., as anyone else. But a culture that insists that loss of sight or hearing is not a handicap (or worse, is something to be celebrated), is kidding itself.
I've seen the battles in deaf culture over the use of cochlear implants, and some of the arguments I find ridiculous. Insisting that a child remain deaf, when the option exists to allow them to hear at least somewhat, just so that they can remain part of "deaf culture", strikes me as being on the same level as those who insist that a black kid who strives to excel academically is betraying his heritage by "acting white".