99.9% of horses, are not afraid of humans, and yes that includes vets,
it is the way they are conditioned and treated.
Whatever you are thinking, is picked up in an instant by your horse, so when you are expecting trouble, it will happen.
A visit from the vet, usually means some form of...
Just be sensible, most healthy ponys and horses can adapet to weight, you only have to visit riders around the world, a small strong animal can carry much greater weights than a tall leggy animal,
A 10 stone bad rider is heavier to carry than a 15 stone good rider,