Some people say that statements like that are naive and stupid and only made by people who have blinded themselves to the reality of the world. Obviously, the average person can't match the performance of an Olympic athlete or the brilliance of a famous scientist or the compassion of a saint. Obviously, some people are disabled and, in the area of their disability they can't match the performance of the average person. Therefore, it's silly to say people are equal, silly to pretend these differences don't exist.
But equality isn't about ignoring differences. It's true that people have different skills. Some people are disabled; that doesn't mean they can't have useful skills. Some people are not disabled; that doesn't mean that all of their skills will be better than those who do have a disability. It's okay to value and celebrate your skills. But it is not okay to declare yourself superior because of them.
Say you are an Aspie and you are really (and stereotypically) good at math. You like being good at math. You want to become a mathematician. You are aware that most NTs stop at algebra, while you are happily playing with proofs. This makes you better at math than most NTs. It does NOT make you superior; it makes you a better mathematician.
Say you're an NT and you are really good at communication. You're an extrovert. You like interacting with others. You have a large circle of friends and you're making connections for a career in business. You understand that autistic people are socially awkward and sometimes have trouble even using language at all. This makes you better at communication than autistic people. It does NOT make you superior; it makes you a better communicator.
And if being really good at something does not make you superior, then neither should an impairment make you inferior.
"Equal" does not mean "equal in skill" or "equal in talent" or even equal in social status, wealth, or opportunity. It means that every person is worth as much as every other person, and should have the same rights, and should be protected just as much as everyone else. It means that every person should have the opportunity to use their skills and to become the best they can become at the things they choose to pursue. It means working toward equal treatment and equal rights for everyone--and it means acknowledging that "equal treatment" is not the same thing as "being treated the same", because people have different needs. It means that no one has to bow to anyone else, but everyone has to respect everyone else.