What do you expect?
The last thing one can expect a biased person to see is their own bias; that's what makes them biased. It doesn't matter whether they are biased right or biased left; it is just bias.
What is disturbing is this insistence by the media that we must be biased either to the left or the right -- and if you're biased to the left, it's not bias. These are not deep thinkers.
The real solution is not more partisanship or even more bi-partisanship but people who fairly see the whole picture. In the media bias, such a thing is not possible.
Liberals and leftists think they are not biased and prejudiced.
They're biased and prejudiced about different things; their worst bias is this notion that they are morally and intellectually superior to everyone else -- which is the greatest human flaw of all.