Memes follow the general definition of art. According to Oxford English dictionary, art is the expression or application of human creative skill and imagination, typically in a visual form such as painting or sculpture, producing works to be appreciated primarily for their beauty or emotional power.

Notice it says typically, not always. This definition includes writing, which is not a very visually pleasing thing, but a more meaningfully pleasing thing. Memes follow this definition just as much as literature or any other traditional art form does.

That is why memes should be acknowledged as an art form. If they are not, this is a direct insult at the entire culture of millions of people who enjoy memes.