Aestheticism, a literary idea meaning much but summed up as "Art for art's sake," is both essentialist and moralist.
It is essentialist in claiming a singular, central, pure essence for art. For the aestheticist, art has but one singular purpose, and thus there can be one singular approach for all people to all art. It requires a commitment to a quasi-spiritual understanding of what art is.
It is moralist in claiming that those who do not follow the aestheticist's approach are in the wrong, and in the wrong in an immoral way. The aestheticist may claim that other approaches to art debase it--by failing to approach a work of art at its essence (as defined by the aestheticist), the individual commits a damaging wrong against art.