When you control a man’s thinking you do not have to worry about his actions. When you determine what a man shall think, you do not have to concern yourself about what he will do. If you make a man feel that he is inferior, you do not have to compel him to accept his inferior status, for he will seek it himself… If you make a man think that he is justly an outcast, you do not have to order him to the backdoor. He will go there without being told; and if there is no back door, his very nature will demand one. ~Carter G. Woodson
Segregation works to build thought patterns this way and to keep people in inferior positions. It works to keep people from questioning and from fighting back. Disabled people are often unable to access spaces because they are physically inaccessible, because they are financially inaccessible, or because of systemic exclusion.
Segregation, maintains Joe Shaprio, author of No Pity "whether the result of stairs or attitudes – creates harmful myths and stereotypes. Worse, it sets up a self-fulfilling prophecy for failure – that disabled people are invisible or separated” and this prophecy acts as “proof that they do not need inclusion or are not even capable or worthy of it."
If disabled people don't go to the store or to the theatre or to school (because those spaces aren't accessible) then there is no reason to make those spaces accessible.