I'm not seeing anything remotely good or cute or cool about this.
This is NOT what they were bred for, and to me it is wrong to do this at all.
There is enough cruelty in the world, do they have to add more?
While I agree with 90% of your post, I even debated on posting. I am not a fan of most diciplines of equine "sport".
I will say that I do not have sound on my computer, so I don't know any of the narrative that was said.
I felt that this was a one time only or once a year event. I doubt that any of these horses are going out on the racing circiut. I saw no horse being whipped, and It was a short track and looked like it was all done in fun.
My Clyde was not bread as a riding horse but I rode him in bareback pleasure classes (had no saddle) often at the local fun shows, nor was he an endurance horse but I drove him in a Combined Driving Event, when my regular driving horse was lame. ( we got a beautiful blue ribbon and a trophy for getting the most penalty points without being eliminated).
So, I agree that there is too much cruelty in this world, I feel these horses were not bred only for their speed, nor will they be discarded after their racing career is over. They were most likely back in their pasture by dinner time waiting for next years race.