I can see your point. If the most important and biggest party of your identity is your sexuality, and nothing in your life is more important than expressing it, improving it, and getting people to acknowledge it, then it doesn't matter what the rest of the platform of any party is - the only part that is important is the part that affects your sexuality.
Most people, however, have many aspects to their lives, and their sexuality is only one part of it.
Those who focus on only one aspect of their lives, and blindly follow the party that appeals most to that one aspect rather than weighing the sum total of the platform may find themselves unhappy with the outcome, even if their one most important desire was met.