"What a bad opinion of Man and of rationality!"
Without rules and laws, yes, sometimes people will behave well. It is probably due to their upbringing and being instilled at a young age with certain values and principles. And, there are people who tend to behave badly despite rules/laws to the contrary (see "America's Most Wanted") and must be corraled to prevent future poor behavior.
Then, even for those who usually behave well, there are occasions when they still behave badly. They get tempted, think "no one will know", that they will escape consequences, that personal benefit outweighs apparent risk. So, even for those people, in the absence of rules (or even with rules in place), they will behave badly, at least sometimes.
I don't know that this is an overly-negative view of mankind, or simply recognition of our fallibility and weakness.
The distinction I make between law and faith is that laws are made by us fallible men, for our own convenience. The laws get bent, distorted and broken because of our fallibility. Religious faith, on the other hand, is based upon God's laws, an infallible entity. Yes, we men still try to distort, bend and break God's word, but that is our fault, not His.
Ever heard the saying, "You can't legislate morality"? That, to me, shows the difference between's man's laws and God's laws. Man is too limited to be able to dictate to people how they should treat each other in so many respects. We do the best we can to try to tell people not to murder or rob. But, God's laws seek to instill in us guidelines for conducting our lives in myriad ways that man's laws could never hope to accomplish. It is up to each of us to allow God to come into our lives and lead us in every minute thing that His will divines. Thus, you cannot compare the laws/rules of man with the teachings of faith.
Getting down from my pulpit now . . . .