From Obsidian Wings:
The genius of Horton lies in what it says about the limits of empiricism and the dangers of mob rule. No one in the mob is on Horton’s side until the Whos prove their existence to the mob’s satisfaction. Until then, every character in the book is against Horton and the Whos. This is aptly summed up by the little kangaroo’s repeated refrain of “Me Too!” to every pronouncement against Horton by the leader of the mob (the big kangaroo).
These are pretty deep themes for any book to explore. Horton is basically an indictment of not only the baser instincts of humanity, but also the better, including humanity’s much-prized intelligence and rationality. After all, the mob, for all its mob-ish-ness, is doing exactly what most of us would ordinarily find praiseworthy. The mob is reasoning from the facts that it has. A mob for the scientific method, if you will. And, yet, there are times when the prudent thing to do is not to reason from the facts that you have, but to accept that you might not have all the facts. And so you should, at least temporarily, suspend judgment. Every time I read the book – and I have young kids, so this is a frequent occurrence – I am amazed at how Dr. Seuss managed to present these themes in all their complexity to a very young audience without dumbing them down.
That actually kind of makes sense.