Free labor isn't slavery, man. Otherwise these people vounteering at soup kitchens, homeless shelters and whatnot are slaves. Sweeping off your sidewalk is slavery. Picking up a peice of trash and putting it into a trash can in a city park is slavery. Man, we are really oppressing the hell out of ourselves.
You don't see any difference between those things, which you can leave at anytime and prison labor which you can't? Not a thing?
As for Brave New World, any society that imploded instead of being invaded, works. Same thing for that happening before the invasions.
Some societies imploded internally because of slavery and totalitarianism. The economy of Rome was destroyed by slavery, for example. Not because the proles drank too much or whatever.
Prison labor isn't slavery either, because they can just sit and read books in their cells or whatever instead of pick up trash on the hiway. They have options besides work and they are probably in prison for a good reason anyways. Prison labor is a privilege, so they can go out and do something to pass the time, it isn't something forced on them. This might not be true in every prison system in the world, but its generally how it works in the USA.
Uncompensated internships I agree are pretty shitty deals in most cases, but its not really slavery, since you could go work for some other company that might pay you. Internships are probably a somewhat unethical business practice. Not quite slavery, you could always say "fuck this" and walk off the job to find something else to do. Slaves can't do that.
As for same-sex couples paying more in taxes. Why is it ok for single people to pay more taxes then married people? Why should the government hand out tax-breaks to heterosexual couples? Why is the government in the business of getting people married in the first place? The entire instituion is baised and discriminatory against singles, so I think it should be abolished as a state function, period. How about giving people tax breaks for having kids and dependants and everyone just has to file their own damn taxes?
Society has a vested interest in keeping people safe, even from themselves. A person being harmed (by themselves or something else) incurs a cost to society, because that person requires care, is less productive, and so forth, and also because the cost society puts into bringing up and supporting that person has less return on investment if that person doesn't live up to their potential, or doesn't live long... not to mention the fact that the person likely has social ties that would be strained by their being harmed.
Your right about that, if you have say state-funded medical care and you are a chain-smoking, hard-drinking, Big Mac eating guy costing the taxpayer money for your unhealthy lifestyle is almost irresponsible in this case. However, if that guy must pay for his own health care, then there is no ethical problem there.
If a guy kills himself, sure he won't provide the society with his labor or tax revenue, but thats a pretty lame excuse for why he should stay alive against his will.
Self-ownership is also abou putting power in the hands of the individual to decide their own fate and make individuals responsible for their own decisions.
As for productivity of individuals, a person probably has already contributed to society in even a short, troublesome life-span then if they had never been born at all. So why should a individual be born with obligations? There is an argument against self-ownership if the society is highly communitarian, like Sweden maybe, where society treats people as long-term investments, but the USA is more individualist and people are treated as ends into themselves, not as means into an end.