Amos,

Rest assured that Young Earth Creationism does NOT hold that, in order to have a code of good and evil, you must accept their beliefs.

A code of good and evil fits well with, and flows naturally and logically from, YEC.

Equally obviously, SOME Ancient Earth Naturalists (Ayn Rand and Herbert Spencer, for example) have had, let us say, some "issues" with good and evil.

However, it absolutely does NOT follow that one can't have a code of good and evil without YEC.   

Kent