Wow... i think the number of neg reps you got shows what people think of your opinions. Well done though for presenting them in a structured manner, better than seeing horrific signs such as 'God hates fags'. I also hate when people use religion as an excuse for hatred so thanks for not going down that route!
Anyway, you also forget about people who simply don't want to have children? Why would nature make them do that?
My view is that we shouldn't mess with nature. If people are gay, or want to be gay then so be it. When you say it should be 'addressed by doctors', it reminds me of sick psychologists that attempt to change a person's sexual preferences. But think of the case of David Reimer, who's gender was reassigned to female, then reassigned back to male but he grew up just feeling wrong, suffered multiple problems and later commited suicide.
10% of people are said to be gay. That means 90% will still carry on the human race, so really from an evolutionary perspective it doesn't matter whether people are gay or not. It's not some disease that will start spreading.
Gay people can be very loving parents, they can care for others' children and adopt or foster. The human instinct to care for children is still present.
How you can even think of comparing paedophilia with homosexuality is beyond me. Pedophilia is a crime, it harms people, scars them for life. Being gay is not, it doesn't harm anyone, only those that can't get over their own bigotry. For paedophiles, there is an issue of right or wrong - what they are doing is wrong but they still do it. Being gay is not wrong, it's just a feeling, who you love, who you want to spend the rest of your life with.
Humans mostly follow their natural instinct, their gut feeling with things including who they are attracted to. When you ask a gay man or woman "how do you know you're gay?", the most likely answer you'll get it "I just know, I've always known" (my brother included). There are very few that will say "I chose to be".