I looked for the same info when I was struggling with my decision. I wanted to hear the other side of the argument. But as other posters have said, there really isn't any good, solid evidence out there that homeschoolers suffer socially or academically-- in fact all the statistics are far in the opposite direction.
I have encountered one adult who regretted being homeschooled-- his parents were very strict and controlling, he feels he was deprived of a normal life. But who knows what would have happened if he'd been in school, he could have had a whole other set of problems. Sometimes I feel angry at my parents for not "rescuing" me from school and HSing me, but again, maybe it wouldn't have worked out. Even some of the weird/ very introvert HSers I've encountered may not have been any different were they in school, maybe they'd be even worse off. It's really impossible to know.
The unions are against HSing because it takes money out of the system and (they won't often admit this) removes many of the best and the brightest from the classrooms. Teachers know very well that even 1 very bright child in a classroom can change the entire dynamic and "lift" the other students up. With millions of bright children, with the much coveted invested parents, opting out of the system, the system suffers. So I guess you could take a social responsibility argument against HSing (which I've seen some on MDC do). The socialization argument about HSing is pretty stupid as we all know, and the child abuse thing is even more stupid.