That's how confirmation bias works, we only see what we want to see. A shockingly large number of my right of center friends still thought that Al Qaeda made millions buying puts on airlines before 9/11 when I asked them, even though it was pretty definitively determined that they didn't. There are reasonable people, not conspiracy wingnuts, and they did adjust their worldview to that particular fact when it was pointed out to them, but until then their brain had just glossed over and/or ignored it. I'm sure my brain does the same, that's why I talk politics with people who have different views than me.
