Thanks to all who helped me with this question.
Here's what I wrote back to William:
Dear William,
Sorry it took so long to get back to you.
We are living in a time when homosexuality, for example, is accepted as a normal lifestyle, even a genetic predisposition. The Bible begs to differ by instructing us that some sexual sins require the death penalty. e.g., adultery, bestiality, (most) incest, etc.
Why so severe?
To ask this question is to pass judgment on God's sentences for various crimes (sins). The fact that these sins require the death penalty is because these crimes deserve severe punishment. For the Bible believer, we learn the severity of a crime by its penalty, not our opinion of what this or that crime might deserve.
Not all sins are crimes punishable by the civil authorities, (covetousness is not a civil crime) but all sins, even the slightest, deserve eternal death in hell. (Romans 6:23) In the Old Testament, many sins required different kinds of sacrifices. For most of the crimes mentioned in Leviticus 20 (and other places) there was no sacrifice for those sins and therefore the authorities, by way of execution, delivered the offender directly to God for judgment.
[some personal items are omitted]
Thanks,
Ed Walsh