Yes, screw up someone's sport and you will be lynched!!! I don't know many sports, human or animal that allow flash.

The second day of that show I had kids coming up saying PLEASE don't point a flash at my horse, he is scared of them!!! The shutter sound scares him! Well, I made a point of being there EARLY and having a pocket full of treats. I also showed the kids my camera doesn't have a flash at all, so, there was no way for me to use one. Then I sat with the shutter in motor drive and the horse sat there not flinching. I then asked if they heard my shutter(gotta love the E-1's QUIET shutter) Made life easier for all

I don't point my lens at a horse coming down a line if it is a spooker.

Lots of unwritten etiquette rules you BETTER know in the dog and horse show rings