The problem is that 90% of people will not do that once they've satisfied their confirmation bias. Hard to say if that's going to be better or worse than the current echo chamber effects of the Internet. I'm still holding out for better, but certainly this is shaking that assumption
So this probably is valid. However, so is Gell-Mann amnesia and both phenomena happen a lot. There are topics where one side is the group of people who have attempted to understand a problem and the other side are people who either do not or won't due to emotions. Acting as if it is all confirmation bias feels good but probably isn't the best way to look at the media.
