Please understand that when you suggest that no one outside a demographic can engage with media depicting another demographic sexually, you are deliberately telling asexuals that they have no belonging in any sexual community. Asexuals have a libido, some can and do have sex.
Asexuals do NOT have a sex-based community that takes the time to explain "this character is asexual" before they masturbate or have sex with their asexual, heterosexual, bisexual, or homosexual (etc.) partner(s). Actions are considered to be paramount in media.