The idea of discussion was that two people from wildly different sides could argue their positions. These days they just see you are not part of "their" group and the discussion doesn't even start. I think the people that are in "their group" are predominantly left and probably black Americans. I don't think the Japanese think in such terms (although the Japanese have one of the most racist societies on the planet (or well, according to some people)).

I think proportionally the number of stupid people online has increased to the point that approximately nobody is left as fschmidt says.