1 - If you need to get your horse out of bed right before racing, you have a point. He ought to walk around for a few minutes.
2 - When I've run sprints, I did it without stretching, or doing some light running building up to faster running, and then sprinting.
3 - When a baseball player sprints to first base, has he spent the previous 10 minutes trotting? When a football player comes off the bench, does he trot for 10 minutes before entering the game? How many pro athletes jog around for a while before entering a sport?
If you want to trot your horse for any length of time before running barrels or doing anything else, that is your right. There isn't any evidence it helps, tho, and it certainly isn't "absolute stupididty [sic] & ignorance" to do otherwise.