In all honesty, the author is right if you understand identity under the more mathematical definition; people's emotional and attraction drives are much more messy than the overly simplistic categorization of 'gay' and 'straight' allow for, and it is a personal choice to override that and deny the minority feelings you have.
In this way, being straight is also just as much a fiction. It is a decision for the sake of (over?)simplification and social pandering to deny minority romantic feelings to the same gender within "straight" culture, and just as much a personal choice.
Are these choices ones people have an entitlement to make? Most certainly. But it is dishonest by any measure to pretend they are not choices.
When it comes to the physical mechanics of arousal, however, there are additional complexities. Sometimes the physical hardware itself doesn't associate strongly or at all with arousal. But that isn't, strictly speaking, a factor in being gay, straight, or anything. It just means special considerations are necessary to the sex.
I can completely understand, though how people, particularly younger people, don't believe that much; too little experience, too little exposure to society-at-large, a lack of introspective opportunity all contribute. But life really is *messier* than simple ideas like "gay" and "straight".
It's better, healthier, to just accept that the extent of what you really know of yourself is that you are an insane ape in an indifferent universe, and live honestly with whatever feelings you discover you have, to at least not deny that they exist even when you decide you aren't going to indulge them.
