Read the text and you will notice that they claim that "Teaching Java, as the only language, is damaging." and that might be true.
Not exactly, the article says also:
The slogan is a reminder of how thinking habits of programmers are influenced by the first language they learn and how hard it is to shake these habits if you do all your programming in a single language.
And i have to admin that this is awfully true.
I started with Basic as a child, took me some years. it was then very easy to switch to pascal (one week) and further to c (another week). After that i thought, well i can learn C++ also in one week. Yep, i read the book in one week. And what i did was a little "C with classes" but i noticed only a year later. year after year i noticed that there is more about C++ then what i thought of. After three years i managed to use STL efficiently, used exceptions properly, managed inhertitance (including multiple & virtual inheritance), did use descrutctores and smart pointer and so on. so i thought it's over, i took me three years to learn C++.
But some years later, i read "Modern C++ Design" and noticed that there is still a lot more :)
to cut a long story short:
the first programming paradigm you learn will influence (limit?) your way of thinging quite a while.