Screwing up fixnum
He doesn't mean that Java programmers are stupid, he means that unlike Java, Ruby allows stupid people to do stupid things.
Look at what Ruby kindly allows you to do:
puts 10 / 2 # => 5 class Fixnum def /(other) self + other end end puts 10 / 2 # => 12
Undoubtably a very stupid thing to do. Java would have complained, because Java does not let you do stupid things like this. Ruby allows it, though.
This is good. It means Ruby is flexible, and that if you can dream it, you can do it.
Questions or comments?