The government should not legislate morality. The government should legislate behavior which harms other people without their consent. That covers not only the obvious crimes of violence, but also acts of fraud, theft, vandelism, contractual violations, etc. These are society laws.
The government should not legislate "moral" behavior such as sexual orientation, forced church attendance, specific systems of belief (religious or otherrwise), any behavior between consenting adults, or victimless behavior, like prostitution and use of drugs, alcohol or tobacco (although the government can certainly legislate the consequence of recklessly abusing these substances, creating potential harm to others in the process).