I saw this in a public school the other day:
It says "Diversity Is The One True Thing We All Have In Common
In a school, where kids are supposed to be learning to think, they've hung this wildly illogical statement. Presumably the teachers pass it every day. Apparently nobody has said "what a lot of nonsense" and taken it down.
If you try, you can say things about unity in diversity that make sense, but spewing garbled platitudes is pretty important to Newfangled People, especially when you compare it to something all crazy and old fashioned like forming valid thoughts.
So they don't try.