Why?
Is there some objective reason you believe them more, or is it just that they tell you the things that feel right to you?
Speaking purely for myself, I find Greenwald and Taibbi to be every bit as slanted and shrill as any other source of media, they're just slanted in a different direction.
Should they be included as part of an overall media diet that, on balance, gives you a more rounded view of current events?
Perhaps.
Should they be believed to the exclusion of other media sources? If you're asking me, absolutely not. That's no better than subsisting on a diet solely of Fox or the Times.
Incompetent people are people who dig themselves into deep holes because they are clueless or crazy. They are not capable of digging themselves out.
Now what happens if such people yank a whole bunch of others into that deep hole? What do you do?
If you are not capable of pulling all of them out sure you can make a big noise and hope grandma or someone shows up to help. But for some problems no one is coming.
And these two fools sell to their fan clubs that grandma will show up if the right noise is produced. For all their giggling and raging, count the number of times that has happened.