Indeed, anyone can edit an entry, just as anyone can flag an entry for being lacking sufficient or valid references to support the claims in said entry. The entry on the Kensington stone cites 40 something references as justification for the statements made in it. Frankly, I wish that more people justified extraordinary theories with multiple citations.
Is your issue with Wikipedia in general, the wiki entry on the Kensington stone in particular, or the sources cited as proof? Have you checked any of those references? Did you find any in error? If so, did you mention this on the talk page for the article?
While it's perfectly true that anyone can edit a wiki entry, don't think that there's no oversight of any sort. Not every entry is 100% correct (particularly when it's a subjective topic by nature, as we may have different opinions of what's truly correct in such cases), but the signal-to-noise ratio on Wikipedia is nearly always significantly higher than it is on blogs, Internet forums, and other social media where no justification is required and peer review is impossible.