Here’s a share from the Kumanichi (local newspaper):
If you follow the links to the main page, you’ll find a montage video of many different horses in the festival:
https://www.youtube.com/watch?v=C_-BtoNeRjk&t=1s
They’re beautiful animals but as I watched, the English phrase “getting jerked around” came to mind. Most of the Japanese-language comments I see on the Facebook post now are positive but one person does express concern about the treatment of the horses.
At the top of the Kumanichi page that has the video is the phrase “飾り馬勇壮” (Kazari uma yuusou) which might be translated very roughly as “decorated horses, bravery.” Personally, I think that the pursuit of this 勇壮 (brave, soul-stirring, heroic) atmosphere leads inevitably to jerking the horses around. It may not rise to the level of “abuse” but, nonetheless, I wouldn’t want to be in the festival if I were a horse.