Where is the line between a disorder and else?

Our moral imperative is to prevent people from hurting themselves because of psychological issues. Amputations brush up against that moral imperative. Being gay does not. You are harming no one, and are in fact improving your life by being involved in relationships that enrich your life.The other problem you seem to be having is that you are confusing two different usages of the word "natural". There is natural as in how nature operates, and also natural as in how something usually operates to the benefit of the body. Those two are not the same.

They are in the wrong. Offending someone's sensibilities is not doing them harm.

There are many people who are wrong about many things.At the end of the day, you are the one living your life. There is nothing wrong with listening to the advice of your family and friends, but remember that at the end of the day you are the one who has to live with your choices. What family and friends are supposed to do is accept you for who you are and support you in your journey through life. If your family and friends can not do this, then you need to find new family and friends to get advice from.