As stated in the post, Norman Geisler lists these 10 points that are used by Christians to justify homosexual behavior. Geisler does not agree with them and neither do I.
Anyway...eunuchs are not homosexual, they are asexual. Isaiah was definitely not referring to homosexuals in chapter 56. Some commentators understand Isaiah to be referring to individuals who have given up the possibility of marriage for the Kingdom of God, rather than to physically castrated men (see Matt 9:11-12).