I'm with the majority here. There is good and bad in EVERY discipline. Have I seen nutter contesters with riders that had no business doing anything at speed? Absolutely but I have also seen (and owned) speed horses that had extremely quiet manners and very level headed.
My old reining mare did double duty and was my go to speed horse as a teen. I could walk her in quietly, she'd stand on the line head down and calm, run a 16 or less pattern and walk as calmly out of the arena as she went in. I could go get her out of the pasture now, blow her out all the way and hand her over to my 6 year old to cool down and she'd not take a step faster than a walk.
There is overhorsed and under trained in every aspect of the horse world. Can't fault the discipline for the poor decisions of some involved in it.
Life is like a camera. Focus on what's important, Capture the good times, Develop from the negatives and if things don't work out, Take another shot.