I believe that there are more than two genders because the gender identity spectrum has essentially three corners: male, female, & agender. A person can identify as any of the three perfectly or they could be somewhere in the middle. I also believe that the gender a person identifies as should be respected because the majority of conservatives believe that gender identity is a choice and should be punished. I do not see why anyone would purposely choose to live a life that would cause them potential ostracism.
Alternative genders largely rely on people wanting attention in another corner of their life. Being transgender is very real, but that still means that there are 2 genders. Agender-ism isn't real, but a new attention-seeking aspect of somebody's persona. Find me somebody who is "agender" or any gender other than male or female that isn't under 25 with piercings and neon hair. 10 or so years down the line, these people will be male or female, or at most transgender. Gender identity outside of male/female/transgender is a choice. Nobody naturally identifies as a toaster or chair.
I actually have yet to meet an agender or genderfluid person who has that lifestyle just for attention. I never said a person would naturally identify as something idiotic as a toaster or chair. Sure, people would do things to seek attention, but only a very small percentage would seek attention by faking their gender identity. I for one should know that gender identity is not an attention seeking choice mostly because I am genderfluid myself and never in the time it took to realize this aspect about myself did it cross my mind of how much attention I would attract. It was a part of me that I have chosen to express.
Are you under 25? I've never seen anybody above that age who identifies as other than male or female. I assume that you are very active in the LGBT community, as most "genderfluid" people are. Is your "genderfluidity" your defining character trait? Deep down inside, you know that identify as male or female, but have told yourself the lie that you are "genderfluid" for so long that you almost believe it. You probably just have a thing for crossdressing, or it's the teenage angst telling you to get more attention. I assume you also use tumblr? Think long and hard about what you're saying. Look at the people around you that are "genderfluid". They often seek out attention, don't they?