In a way that's true. I mean, nothing can be the real truth, so of course Wikipedia can't. They do have an enormous effect on the way things are presented, though.
But is that a bad thing?
Here's the link to the Naked Shorting page at Wikipedia. It briefly mentions that Overstock was involved in a lawsuit, but it's a drop in the bucket compared to the whole page. Seems okay to me. It's not like Wikipedia is somehow denying the truth by not providing a soapbox for Bagley and Byrne. It's not like Wikipedia is somehow denying the truth by not having a page dedicated to the details of that suit either.
A case can be made that the things that are being left out are either not part of the objective truth, or not important to the overall general truth. One can get a pretty good beginner's grasp of the issue without knowing what is missing. It's when you want to go deeper that the opinionated and detailed sources become important. Wikipedia is a first stop, not a one-stop. A better question would be whether it succeeds in this capacity or not. I think it does.