While I agree in large part with your post...it's also surprising that so many liberals flock to HuffPo and Daily KOS for their "news".
I would say that the liberals I know treat the Huffington Post and DailyKos pretty skeptically. I know I wouldn't trust either to give me the full story. While HuffPo is certainly liberal, my biggest complaint with them is their absurd bias towards sensationalism and Kos is usually less sensational but even more liberally biased.
So yes, I agree that a nontrivial percentage of liberals get their news from non-credible sources like the above but I don't think the proportion is close to as large as with conservatives. I also think (as the chart shows) for all their faults HuffPo and Daily Kos retain at least a general tether to reality, unlike Infowars and Breitbart.
