Rubyists most certainly DO hang themselves with monkeypatching, quite often. You just don't tend to hear about the ones that to that, because the sites they build that way don't survive long enough for anyone to notice, assuming that they even launch them successfully, which is rare.
I think in fact that because Ruby is a much more forgiving language than, say, C++ (the same goes for Python), the average caliber of Ruby developers is FAR lower than the caliber of, say, C++ and Lisp developers. My experience with Ruby and Python developers hasn't been positive -- in fact, working at a Python shop gave me an intense distaste for the language, and my experience at a Ruby shop lead to similar sentiments among a lot of the senior developers who worked there.