Yes the XBox 360 has more headsets, which means more idiots can be heard, but I definitely think the Xbox 360 also has more idiots because of an overall younger fanbase.
The 360 has always been the cheaper system, so high school kids are more likely to own it and parents were more likely to pick it over the 360 for their kids as well. Although the peak of stupidity for me was Halo 2, got to a point where I only played private matches. (which were all-around more fun anyway)