In my own experience, I have been impressed with the fairness of the Wikipedia articles that I have seen.  But then again, I tend to look at articles on weird, off-the-wall subjects like Compsognathus and allied small predators of the late Jurassic Morrison Formation, in which maybe five people in all the world are keenly interested, and the systematics of Indo-European languages of Bronze-Age and early Iron-Age Anatolia, in which maybe three people in all the world are keenly interested.

But then again again (!), for those eight people at least, the way that those subjects can be presented in Wikipedia might most certainly be "controversial."

The examples of biased editing that you cite are all of them unethical, especially the one that assigns blame for the Alaskan native people's bankruptcy on themselves, not on the Exxon-Valdez oil spill.  But I was under the impression that biased descriptions and accounts tend not to last very long in most of the more frequently visited Wikipedia articles, precisely because they will be re-edited by readers with an opposing perspective, who will quickly be aware of bias.

Chickens deserve our true friendship! So do fish! So do other sentient beings! Let us learn to be kind.

"Someone tell the co-op student to head over to an internet cafe and remove all this embarrassing stuff..."

a sibilant intake of breath

On the other hand, I have not read that any assignment involves having to edit a Wikipedia article already in existence.  But it would not surprise me if that has been happening.

Could that sort of thing lead to mischief, misinformation and mayhem?  Oh, sure.  But the managers of Wikipedia seem confident that the public-forum aspect of the thing will sort out all that M,M&M stuff.  In time, at least.  Meanwhile, as with everything else online, it is reasonable to be suspicious.

Chickens deserve our true friendship! So do fish! So do other sentient beings! Let us learn to be kind.