How dare you tell a handicapped person not to do whatever they can to enjoy things that only capable people can. I have MS and love the idea of an assisted bike so I might get some exercise and enjoy the road/scenery/company of others. I accept the "risks"you mention. Doesn't everyone that rides a bike? 
Don't be a jerk and insult an entire group of people. Life's not easy for many of us but that doesn't mean we don't want to try and be a part of it.

Labels: moderation: toxicity, insult