Asexual is not a mental illness, and the very fact that you would go there is emblematic of the way asexuals are excluded, rendered invisible, and otherwise marginalized by sexuals.
No, I didn't exclude them. Sick people are very much 'with us', and can be quite visible as long as they're ambulatory or functional - in point of fact when they go on killing sprees they become quite the center of attention.
True, they're 'on the margin', but after all, isn't it true that the vast majority of people have a working gonad and a brain connected to it?
Do you consider homosexuals to be mentally ill as well? Both are sexual minorities who deviate from the "mainstream". What's the difference?