I'm not doubting that you can be judged socially for saying you're asexual but is it really the same as being gay or lesbian?
Although I agree that it shouldn't be classed as a MH condition, I've never heard of anyone being denied a job or housing for being asexual or being beaten up or taunted in the streets.
And what extra legal protection/rights do asexual people need? Surely they have the same rights as anyone else?
www.stonewall.org.uk/about-us/news/new-research-shining-light-‘dehumanising’-discrimination-faced-ace-people