I read that the Shias do believe that non-Muslims are literally najis. They used to be forbidden from going outside in the rain by the Iranians (or Persians more probably) so that they would not 'wash onto' any Muslims and makes them impure.

I don't think Sunnis do think this in that sense at least.

But then wikipedia's articles are not exactly brilliant Islamic Fatwas, so you should find a real scholar rather than what ol' Jimbo Wales has to say...