Where is it done humanely? If the horse is happy and not being abused up until their death, then go ahead.. But I've only seen videos of inhumane places, where the horse is desperately trying to escape but ends up getting hung up on a rope by a leg, blood dripping down to the floor.
I've seen more than one slaughter house in real life, and neither one was abusive or uncaring to the animals.
Scared, nervous, tensed up, and malnourished animals make for bad, spoiled meat, which is why a good majority of slaughter houses actually do care for the animals. Don't let some stupid video made by brainless "animal lovers" brain wash your mind.