I'm mostly a libertarian, because I agree with Democrat's liberal policies on individual rights and I agree with Republican's conservative policies on the role of government.
Americans don't talk enough about the role of government and law.
Just because you happen to believe that something is wrong or immoral doesn't necessarily mean that there should be a law against that something. Your idea of morality might not match mine. I believe that there are a very few basic principles that should be used to test whether or not a law is reasonable:
Grown-ups must be held accountable to their promises. I think there are a lot of bad laws that try to protect people from themselves, eroding the fundamental idea that people should be responsible for their words and actions.
Harm is easy to understand: shooting or stealing from somebody causes them harm. So does forcing somebody to sign a contract by holding a gun to their head, or tricking somebody into paying for something by lying about its features.
Understanding risk is harder. Insurance companies are proof that it is possible to put a price on risk-- your home or auto insurance bill is a measure of how likely it is that your home or car will be destroyed.
Outlawing a behavior is reasonable if we can measure the amount of risk and then weigh the risk against our fundamental right to freedom of action. Only actions that pose a clear risk to the well-being of innocent bystanders should be illegal. But risky actions between fully-informed, consenting adults (like playing rugby) should be legal.
Should it be illegal to yell 'fire' in a crowded theatre if there is no fire?
Yes. Yelling fire in a crowded theatre poses a clear risk to everybody in the theatre-- the risk that they'll be injured or killed in the resulting panic.
Many people think sex outside of marriage is immoral, and that it puts oure society at risk; that sex outside of marriage spreads disease and generally promotes moral decay. Should it be illegal?
No. Sexually transmitted diseases aren't caused by sex outside of marriage, they're caused by microbes. Requiring an infected person to inform their partners before engaging in sexual activity is reasonable; there's a clear risk of harm to the partner.
What about drug laws? Drugs cause direct harm only to the people who (voluntarily) take them-- except for smoking, of course, where second-hand-smoke causes harm to unwilling participants. Are the risks to others tangible and quantifiable?
Certainly taking drugs is risky behavior. You're more likely to end up in an emergency room, more likely to crash your car, more likely to steal to support your drug habit.
But criminalizing drugs also causes problems. Drug dealers shoot each other (and, occasionally, innocent bystanders) and billions of dollars are spent on catching and locking up addicts and dealers.
My opinion: drugs should be legalized, but taxed according to their cost to society. Drug users should be free to sue drug companies for damages caused by their products, and drug companies should be free to decide whether that potential liability would be outweighed by demand for their product.
Imagine cigarettes and tobacco companies, if the government didn't subsidize tobacco farmers and the courts recognized the risks of tobacco and were willing to make the tobacco companies pay for that risk. Insurance companies have recognized that risk for years-- life insurance costs more if you smoke. Assessed risk should be a cornerstone of our legal system.
I disagree with most libertarians' position on gun control (follow this link to the official libertarian party position).
I don't want my neighbor to store nuclear weapons in his garage. There is a point at which the risk to my life outweighs his right to keep and bear arms.
I believe the risk of harm to innocent bystanders from handguns, assault weapons, hand grenades, and nuclear weapons is greater than their benefits to their owners.
Rifles (with clips limited to 6 bullets, maybe; if you need six shots to bring down an animal then you need to spend less time hunting and more time at target practice), knives, slingshots and water pistols are below the line. Your line is probably different than mine.
By the way, I know the U.S. constitution says that, in order to maintain a militia, the people should have to right to bear arms. Blind adherence to a document that is over 200 years old seems a little strange to me. After all, the world has changed a lot in the past 200 years. I'm pretty sure the Founding Fathers would agree that The People shouldn't be trusted with nuclear weapons (and no, I don't really like trusting the government with nuclear weapons, either).
I'd actually have absolutely no quarrel with you if you want to insist on owning the kinds of armaments that were available back when the constitution was written. I bet it is pretty hard to kill more than 2 or 3 people if armed with nothing but a muzzle-loaded musket.