I'm thinking you missed the point of the question.I've given the statement above quite a bit of thought and what I have to say about is this: You say:"Can you explain why homosexual behavior is bad, apart from the fact that the Bible says do not do it?." The Bible also says to not steal, commit murder, adultery, etc... So according to your way of thinking; all these things aren't bad just because the Bible says to not do them. Murder is not bad, stealing is not bad, adultery is not bad; I say you are completely off base and have no clue.
As far as your last paragraph about birth defects and such, God has had every moment in time planned out long before we were here. Oh, we have free will to make our own choices after birth, but the Bible states that God knew us even before we were even thought of, therefore He did make us exactly how he wanted each of us to be. What you don't seem to understand is that God uses all of these things good or bad for His ultimate plan which we can't even begin to comprehend. I have had many a handicapped person touch my life in ways that would have never happened had they not been handicapped. These people who are born with defects are an inspiration as long as they don't sit around and have a "Oh feel sorry for me" attitude. Just think of all the handicapped folks who have made a huge impact on this world in science, music, mathematics, etc... Yes, God has had all of this planned before the beginning of time. Sorry to disappoint you and your theories.