The poll is flawed.
How so? The poll has both sides of the political spectrum, without referring to one extreme or the other. If I'm slightly right of center, that still qualifies as conservative. The poll makes no judgment about the position.
People tend to view things based on their own reference point. A conservative views MSNBC is liberal, but a hardcore left winger might not agree. If even the liberals view NPR as liberal, that shows beyond the shadow of a doubt that it's liberal.
