I think the concept of riding a bike is as metaphoric as you can get here. It shows that the idea of putting one foot in front of the other and asserting oneself in order to move forward is universal -- not just applying to the momentum of a thing on wheels.
To be a disabled child, or a disabled adult who needs supportive care, is to know that your life is literally in the hands of the people you rely on to love and care for you. And those people may well think that murdering you would be doing you a favor.
Today is Blogging Against Disablism Day, an event organized to explore ableism/disablism and their larger social impacts worldwide. Disability hate crimes are just one of the many issues faced by the disability community.