The Bible is a written work. While I believe the Bible was inspired by God, it passed through humans prior to being written down, in many cases multiple times. Like a piece of literature, the context of the work must be considered in the interpretation. I believe the sections interpreted to condemn gay sex are due to an innate lack of understanding of homosexuality.
In many societies, even ranging into pre-Revolutionary France and beyond, people participated in orgies where they indulged in considerable amounts of alcohol and other substances prior and while engaging in random sexual acts. These partiers would indiscriminately cross boundaries of natural attraction, gender, and inhibitions in their debauchery. These types of affairs are what is being condemned.
In contrast, homosexuals are born with the innate attraction and instincts towards members of the same sex as heterosexuals have towards the opposite sex. If you believe God created everything and that all creation was good, then it conflicts with believing homosexuality is bad, since God made everything, including homosexuals.
On nature...
It is just as unnatural for me to have sexual relations with a woman (believe me, I tried, and my ex-girlfriends always said I lacked hormones) as it is for all the heterosexual males here to have sexual relations with a man.
Looking back, these instincts and attractions were with me from the earliest moments of puberty (while other guys were looking at Playboys and SI swimsuit issues, I was collecting men's muscle magazines.) When I finally passed through the denial phases, it was a total DUH! moment. Most gay people I know were the last to realize their homosexuality, most of the people around them figured it out first.
I cannot resist... 21psi2300...
What makes you think receiving anal sex is painful? I'll only say it's not and leave it at that. If you really want to discuss it further privately, I'll be more than happy to. After answering my grandma's questions, I have no embarrassment discussing it.