well, let me tell you that you are most likely not going to have any success by stating that. Not to mention that manipulating semantics is quite complicated in order to change the term in the broad sense. Brony might have had any specific connotation in the past that was describing a specific group (mostly male adults) but over time, it has been mostly reduced to a generic terms that establish one common thing: a person who watches FiM or consumes/creates content related to MLP, for the most part the 4th generation (the most successful one).
I am not against your terminology of horsefuckers not being the same as bronies. The thing is that you are correct for the wrong reasons:
Brony is the accepted canonical term that universally describes a person who spends time and consumes content that comes from the 4th gen, it simply offers a generic name to associate the community in a broad sense indifferently, it simply describes the practice no matter who you are. Horsefucker however, is a more specific term that is only used in the channer circles. Therefore, as it is more specific, it doesn´t describe the community as a whole and thus, if the term becomes a standard, it will fall under a brony subcategory just to describe the slang used within the channer circles at best. It cannot replace the word brony unless everyone else in the community agreed on the term and adapted that term (but then, it would suffer a normalization for being so widespread and the term would lose its original intent after its initial hype). In order to achieve that, you would have to go beyond these circles and expect that other people fully adapt and accept the term over time. This process happened to the term Doom-clones, in which over time got replaced with the term First Person Shooter (FPS) in order to describe that genre of videogames. Other words however, were meant to be changed like the Metroidvania genre or Roguelike games yet no other alternative words/terms have arisen in order to replace them.
