When I played rec sports as a kid, we weren't allowed to keep score because it might lead to bad feelings and competitiveness. Not just when we were too young to do it right, but up to around age 15. Everyone involved did keep score of course, we'd all signed up for a competitive sport outside of school. (Or been pushed in by parents, who nevertheless didn't want scorekeeping...) But anyone overheard mentioning the score got an angry lecture, so we had to do it when there were no (adult) witnesses.
It didn't take long at all for kids to notice that we were 'protecting' the adults instead of the reverse. Score was still kept, kids were still being bullied to tears over losses, nothing had changed, but the rule worked perfectly at making sure parents and coaches didn't see it happen.
I don't think participation ribbons hurt kids, because they have so little impact. At worst, aimless positivity is just a wasted opportunity for something better. But the more controlling side of self-esteem building is creepy and terrible - it has a horrible emphasis on changing kid's lives to allay their parents fears, no matter how unreasonable.
"Operant conditioning"?
For whom and for what purposes are our kids to be satiated, scheduled, individualized, and zoned?