For me, mises.org has the same credibility in economics as the DailyCaller or PoliticaUsa have in politics.
Same here. I used to read articles from mises.org, but they seem to have some fishy characters as contributors and authors.
Note, however, that Menger is not a columnist or blogger: http://en.wikipedia.org/wiki/Carl_Menger http://www.britannica.com/EBchecked/topic/374958/Carl-Menger
If you want a more accurate description, I recommend the first half of David Graeber’s book Debt: The First 5000 Years, also mentioned by another top-level comment.