>>46625568> It has no business being psychic at allAll the moves and abilities with the word Magic in them are Psychic Type. G. Rapidash focuses on the part of unicorn lore about them curing poisons and Psychic is SE on Poison.
Also I was hoping we could get through this thread without mentioning MLP, but with how popular and influential it was I suspect that yes in fact G. Rapidash is probably inspired by MLP if only slightly. All unicorns in that show have telekinesis, which in Pokémon is a Psychic thing.
Furthermore the Psychic Type is sometimes based on love and emotion, rather than brainpower, as evidence by Gardevoir, Swoobat and Latios/as as well as the moves Heart Stamp and Heart Swop. They have psychic empathy, i.e. telepathy. They sense thoughts and emotions.
As a Psychic Type it's easy to explain why G. Rapidash can sense approaching danger in the form of premonitions, and why it can "peer into your heart" and determine whether you have evil intentions or not. And finally it's just sort of this basic idea of a unicorn having a horn. It's attached directly to its forehead, so you can easily imagine the horn connects directly to its brain and lets it use psychic powers that way, like a big ole antenna or a magic wand.