Playing sports in high-school and college I had several coaches that acted this way from time to time. Everyone is different, but it never did anything to motivate me. Like others, I just mentally checked out during the rant and focused on the next race, game, etc.
I think the fact that coaches jobs (tenure, pay, etc.) are so results based that you get these melt downs every so often from someone feeling the squeeze. Do I think its warranted? NO.
It's basically a caveman style approach to motivation, with fear as the primary driver. And, kids are softer today than the previous generation but we are softer than the generation that came before us as well. It's a by product of an advancing society.