>>46182693A few.
For starters, Galarian Rapidash AREN'T telepathic. Being a psychic type doesn't automatically give you the ability to speak in people's heads. The reason Gardevoir is often portrayed talking to humans this way despite never doing it in canon proper is only because it's hidden ability is quite literally 'Telepathy'. Rapidash, in either of it's variants, is never shown, said, or even alluded via moves it can learn to have this ability. It can't communicate directly to humans. It's arguably not even shown to be super intelligent, as G-Rapidash's entries focus more on it's physical feats and call it prideful (i.e., arrogant).
Two, it's a Pokemon, which are effectively the animals of their world, and are owned as "pets" by trainers. This would be a social issue as you have influence over their entire life, like a boss coercing a staff member into sleeping with him for "benefits" and firing them if they refuse. The Rapidash wouldn't really be able to refuse since you could effectively force it into unwanted relations due to your status over it as the "trainer". This is, quite literally, raping a fucking Horse. And if I need to explain to you why bestiality is wrong then you're fucking disgusting and already a failure of a human.
Three, this feeds into an unhealthy interspecies relationship that would be damaging mentally and possibly physically for both parties involved, though the Rapidash would comparatively have it worse, with behavioral issues being worsened. As you cannot communicate with the Rapidash, because it cannot fucking talk, the relationship would either fall apart before it began or be based entirely around sex, which is extremely unhealthy and would lead to heavy dependence issues and possibly aggression.
Also all the other issues with trying to have a relationship with a fucking horse such as all the money you'd need to spend for "accommodations" leaving you broke unless you just kept the damn thing in a ball or the shed 
