Is there a particular issue or problem or hypocracy that you find in the LGBT-community?
Do you feel that an aspect needs to be changed? Do you think something which was changed, needs to return to its original form? Do you think its perfect the way it is? Do you think it will have an impact on something in society?
Anyone of these questions could lead you to a possible essay topic. Then whatever answer you come up with, you must then motivate and defend in your persuasive essay.
Always remember to specifiy your topic, the more general your topic the more difficult it will be to write about, but also keep in mind the availability of evidence, as being too specific will limit that too much (The difference between writing on the topic 'the universe' and 'the mating habits of red ants after a blood moon'.)