This article swings both ways. The first paragraph presents a conservative bias that, while definitely a goal of this medium, goes beyond clever and sounds silly. The second paragraph makes a valid point that conservative estimate usually connotes a lower bound on a number whereas a liberal estimate will be more extreme (and thus often larger), and it is true that neither of these estimates is usually correct. However, from there, the author of the second paragraph moves into blanket statements about Conservatives being depressed and depressing....?
Partial removal suggested, and other changes
I would suggest removing completely - or at least rewording - the second paragraph of this article. The words "conservative" and "liberal" do not necessarily have to carry a political meaning, and the article is not clear about that. For example, "a liberal interpretation" means "a loose, not literal interpretation", and not necessarily "the interpretation of a liberal"; likewise, a "conservative use of natural resources" does not imply the use that a conservative would make of them, but an use "tending to conserve, preservative". I feel that the second paragraph is not clear enough about that.
Unrelated to this, I suggest two other changes. Firstly, the word "cautious" and "avoid" are repeated too much in the first three lines. To alter this, I would suggest changing the second sentence to "... a liberal estimate would not be afraid to overestimate the quantity in question", but I am sure that you can find an even better wording for this as English is not my mother tongue.
Finally, I would add a comma after "for example", but that's purely cosmetical and very minor :)