1. Evolution is a process of constant mutation. Some mutations have a positive effect, and others do not. All have a cause and effect that scientist seek to evaluate. They are not benign as you attempt to insinuate.Finally, I would like to add that even though you may view gayness as a defect, not everyone shares your opinion. Just as left-handedness isn't viewed as a defect by most people today (it was in certain societies in the past)
Not acknowledging one's left-handedness is trying to write with your right hand anyway, rather than developing healthy writing habits with your left.
Not acknowledging one's homosexuality is trying to get into heterosexual relationships anyway, rather than developing a healthy relationship with someone who you can love back.
2. Additionally, homosexuality relates to sexuality while left-handedness is believed to relate primarily to survival. They are a repeating mutation.
Here is an example of a overview of left-handedness. You find me a similar one on homosexuality.