[...] Frankly, I think a language (or style) can be OO even without polymorphism. Granted, you're giving up a huge potential advantage.
I'm going to respectively disagree on this one. Of the two notable features of OO (inheritance and polymorphism), I find that it is polymorphism that most greatly defines the OO style. Take inheritance out of an OO language, and you can still do most of the things that OO enables. Take polymorphism out of an OO language and you are dead in the water.
In fact, I will assert that it is runtime/dynamic polymorphism that is required. Static/compile time polymorphism isn't enough.