In my experience lots of folks educated at top top tier institutions are pretty humble about it, and acknowledge places where other institutions are as good or better than their alma mater. A coworker of mine recently got his MBA from Penn which is not only Ivy League but consistently ranked top 2-3 MBA programs in the country, and currently tied with Stanford for #1 according to USNWR. He never brings it up, doesn't really talk about it much when it does get brought up, and I don't think I've ever heard him criticize anyone's education or experience unfairly (we've sat on several hiring panels together).
The problem is when you go to a good-not-great school. If the top 10 schools for a particular program are considered "Tier 1" the people who went to #15 or #20 are going to be absolutely horrible to work with. It's like they think they need to prove they could have gone to a better school but didn't for whatever reason.
I avoided this trap by only going to small schools nobody has ever heard of.