But in that particular token-buying ecosystem, nobody else can buy that gif. Unless they change a pixel value, or some bit of metadata.
Suppose you actually approached the author of the gif, and bought the exclusive copyright to it, conventionally. The gif itself is still not affected any more by that transaction than of the non-fungible token purchase. Exact copies of it exist all over the place, shared by people who don't care about your copyright.
Also in that particular token-buying ecosystem, you can sell yourself the token representation of that gif multiple times, in order to fool people into thinking that there is a genuine market for the token corresponding to that gif.
Suppose you actually approached the author of the gif, and bought the exclusive copyright to it, conventionally. The gif itself is still not affected any more by that transaction than of the non-fungible token purchase. Exact copies of it exist all over the place, shared by people who don't care about your copyright.