Who cares if some "outsiders" don't approve of the terms of this loan? Its none of their business. End of story. A fundamental difference that sets libertarian's apart is the fact that we believe people should be free to make dumb decisions.
Lots of statists think cannabis shouldn't be legal because its stupid to smoke dope. And we don't want to offend them, right? So lets all stop writing about cannabis legalization on the web due to the fear that it may push others to lose "trust" in libertarianism.
And don't forget that some "statist outsiders" absolutely HATE gay people and don't approve of gay marriage contracts. Should we not stand up for the right of gay people to get married? "Well, of course we should stand up for gay rights and pot smokers, Tom. But what we cannot stand for is high interest rates! You see, gays and wake and bakers are smart enough to make decisions, but the rest of us need a fucking nanny to look over our shoulders."
And why should all contracts have to certified by a third party? If I go to the grocery store and buy a potato, do I need some third party person there to make sure that I'm not over paying? Really, do I? Or what if I bought a pack of cigarettes? Do I need some third party to tell me that they're bad for my health?
Your fear that others will make the wrong decision given the freedom to do so reminds of a Huffington Post (I think) article I read a while back. The author claimed that Ron Paul was literally like a "crack dealer" when he proposed allowing young people to opt out of social security. Guess what? His reasoning was the same as yours.....he fears that people will make the "wrong" decision and not save for their retirement, just like you fear that borrowers will make the wrong decision and agree to high interest rates.
Back to the original transaction......This loan couldn't have been more simple. Borrow "x" dollars, pay back "y" dollars on this date. Do you think Boner Joe is a total moron who couldn't understand those terms? If so, then perhaps you should offer to run Joe's life for him. Just make sure you get the contract looked at and notarized by a third party, of course.
And what is this, "you guys make a great argument for people needing government protection." How am I making an argument in favor of government? Is it because of my view that people should be able to make their own decisions even if other people think they are stupid? To be honest, if you can't handle the thought of people making piss poor decisions in life, then maybe you should consider another ethical/political philosophy.
I hope you stay here, though. The statists have plenty of nannies attempting to control my life already.