Again. Those things happen anyway. Sometimes outrage at laws and restrictive environments lead to them.
Worrying about WHAT IF and then stripping rights is a slippery slope. You pick one, it leads to another, then you are where we are now where people can dictate what you are allowed to put into your body, whether you can sell your body voluntarily for sex, and any number of other things. The thing is the laws don't actually stop it from happening now.
People think of those things because of examples of them happening and people being appalled by them. Being appalled would be no different if the laws did not exist.
You cannot FORCE morality on people. You can make them not feel free and make people who otherwise might not do such things embrace things like bombs.
It is just like guns. Making them illegal doesn't stop someone who intends to use them to kill or commit a crime from getting them. It is no deterant. It does restrict those who have no intentions of doing such things, and they also can't have one to now defend themselves from the criminal.
The laws don't prevent shit. In some cases they instigate it.
If you said no seat belts, I'd say fine, it's your life until you are thrown through the windshield as projectile into the other car, but mortality rates from car crashes are ever dwindling. Consensual sex with a eighteen year old, how about 17...16?...15?...14?... Laws draw lines, and people still disobey them, and some are enforced much more lax then others. In Canada, smoking weed may result in the cop asking you to but it out. Driving 120 km/h on the 100km/h road is the norm, but at 131, they will pull you over and can use the fact that you were 30 over to demerit your license and charge you, at 150 they will automatically impound your car and suspend your license. Things like driving are a privilege, not a right. You are using public infrastructure and thus are bound by public law. If you have your own property, a ranch, and you want to get shitfaced and drive 95, I think no one should be allowed to stop you, however if you leave your property, you are entering society, and society has rules in place to protect everyone's rights. Not everyone can handle a car at high speeds or avoid them, traffic lights are in place to keep an orderly flow of traffic, though are much better substituted with roundabouts. To say laws cause crime may work in cases of drugs, I have no problem saying the way pharmaceutical and other drugs are distributed in our society is a system that fails to deal with addiction instead opting to punish consumption. One of the hurdles we are facing with the upcoming legalization of marijuana in Canada is the ability to properly check for impairment to keep people who are not of capacity to operate a vehicle to be putting every passing car in danger that they become the victim of a misjudgement. I'm a very liberal person, but this is a little too left for me. I view as the difference between a conservative and a far right Orwellian society. But hey, whatever floats your boat as long as it doesn't sink mine.