I’ll break this out:
‘“horse f###er” implies its bestiality, which it may or may not be.
Why “may not be”? Well, “best” implies “beast”: an unintelligent form of life. “beast” would imply the creature cannot speak, build, or form advanced communities (such as towns, cities,advanced governments, etc.).
Now, C.S. Lewis’s “Chronicles of Narnia” does feature what he calls “talking beasts”. They can speak, but as Qui-Gon Jinn in “The Phantom Menace” states: “The ability to speak does not make you intelligent”. As such, though those creatures can speak, they lack the other abilities that would otherwise make them intelligent (aside from, say, centaurs & fauns in the series).
The MLP ponies do carry the ability to speak, build cities and citadels, have advanced form of government (an absolute-monarchial position held by Celestia) and form advanced social communities, with an economy. In short, they are intelligent. Therefore, the term “beast” may not be applicable.
The main issue is that in Real Life, there are no creatures (that we know of now) that are intelligent as the homo sapiens. Therefore, the prospect of inter-intelligent life mating is not particularly thought of. The nature of the equines in the show makes it the target of “beast” though if they existed in real life they may not be.
However, there is an interest in communities (especially online ones) with other forms of intelligent life. Star Trek and Mass Effect both feature other “intelligent” forms of life other than humans (if I remember, protagonists in both do/can do things with these creatures). And remember that MLP is a cartoon. This feature throws most things about reality out the window.
Lastly, I think that most of the clopping bronies are fully aware of the fictionality of the characters.
Why is this important? Because its less likely for them to go out and do it in real life (where it would be seriously taboo). Sure, there are body pillows and that Lyra plush, but those are not real horses, are they?
I don’t clop, or take enjoyment out of sexualzations of MLP, but I just wanted to sort that out. No, it’s probably not what many would call morally correct, but it’s not what they think of. The issue for them really should be more “jerking off to fiction” rather than “jerking off to an animal” (pardon the terminology).’
Though, at the same time, it doesn’t make it less weird or taboo. I would have no problem if I were to do anything with a human Chrysalis, but the regular one…that’s going to take some thought, and I’d probably not do it.
Now, if I were a pony, then of course, that’d be a different story. Being fully intergrated into the culture, I guess things are different (of course; I’m a different species all together). Being such, I guess gender preferences are all that count here, considering I’m a pony and so is everyone else.
Would I go? At the same time, that take’s thought. To do so is to pack up and leave all you have here and start from scratch over there. Though an overall better society, one will have initial problems adjusting to it. If one get’s through this, sure, all is fine, but you have to consider how much you’ll leave behind, and think if it’s worth it.
You really expect them to draw that stuff in the show? I’d assume Mammalian reproduction does include those things, but I’d doubt they’d ever consider showing ponies doing it. There’s R34 for that.
Though as funny the thought, I doubt wings or horns have anything to do with their reproductive system. If they have anything to do with their sexuality at all, it’s probably a sign of arousal. Other than that, headcanon states it’s like every other mammal from there.