Scriptural Background of the Sexual Boundary According to Leviticus 18 & 20

For many Christians, homosexuality and other human sexual orientations present thorny problems for the faith journey. The unfortunate part of this issue is general lack of knowledge of the scriptural content, and uncritical use of the texts of the Bible. Many listen to the preachers and take their words whole, and parrot whatever has been heard.
This is not how we should base our understanding of the scriptures.  If we read carefully the Leviticus chapter 18, the purpose of listing all the "don'ts" has been clearly expressed: Do not follow “their” practices:
18 The LORD said to Moses, 2 “Speak to the Israelites and say to them: ‘I am the LORD your God. 3 You must not do as they do in Egypt, where you used to live, and you must not do as they do in the land of Canaan, where I am bringing you. Do not follow their practices. 4 You must obey my laws and be careful to follow my decrees. I am the LORD your God. 5 Keep my decrees and laws, for the person who obeys them will live by them. I am the LORD (LEV. 18:1-5).