I've always felt that it is a choice to some degree, but not a choice over the feelings you have. As you said people start out gender neutral, and it's my theory that everyone is somewhere in between gay and straight. Not many are completely one side or another. We then choose whether we want to be seen by others as straight or gay. I'm sure there are many people who have some sexual feelings towards members of the same sex, but suppress these and live their life as a straight person.
So in regard to one's feelings I agree that you really have no control over them, but it's my theory that everyone does make a conscious decision on which feelings they bring forth and which they hide deep down. So everyone makes a choice on some level.
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