I added emphasis to another part of his quote, no less valid or important than your emphasis. (Personally, I'm more of a John Adams fan than a Jefferson fan.) Nevertheless, divining the intent of the Founding Fathers is dangerous for the Libertarian, because it's like divining the intent of those voters in Florida. This quote you cited somehow didn't make it into the Constitution, which was a group effort and the product of debate and compromise and finally mutual agreement among the group, as well as among the various state legislatures that ratified it. Look, the whole point here is that reasonable people can differ on interpretation. Just as we have a gazillion denominations because of differing interpretations of the Bible, so we have different political parties due to differing interpretations of the Constitution. As citizens, you and I are equals; we have all agreed to this system of government under the Constitution, and we have all agreed as to the methods of resolving our disagreements over interpretation--at the ballot box and through the Supreme court, which has appellate jurisdiction as to facts and law(with certain exceptions) under the Constitution.
I'm sure Jefferson did not intend that to mean laws such as mandatory seatbelt wearing and drunk driving laws (obviously those things did not exist back then, but I'm referring to laws of that type). For, taken to its logical conclusion, liberty could be entirely regulated out of society in the name of prevention. In other words, if you're drunk and accidentally stab me with a pitchfork, you'll likely be convicted of involuntary manslaughter--but there is currently no law forbidding such an action, nor should there be. The same principle works in the cases you've mentioned: the law proscribing punishment for the resulting act is sufficient.