Drugs are illegal. Doctors go to medical school for years. Even to get a driver's license, you have to wait six months (ostensibly training to become a better driver) before you are fully licensed. So there is already a significant barrier weeding out the worst.
You can't commit murder with tobacco smoke, unhealthy eating habits or lack of exercise. A gun is a weapon. It has its uses, but it's a weapon.
Baseball bats aren't the next most popular weapon in murders. That's an internet myth. You don't even have to look it up, just think about it. Of the most recent murders you've heard about, how many involved people being beaten to death with a baseball bat?