The article does have a copyright notice at the bottom of the page, without any added explanations, so presumably "normal" copyright law is applicable.
There is some disagreement as to how copyright law applies to material that is already posted on the internet at a freely accessible site. Generally speaking, you should treat it as printed material and link to the site, because the site may gain some benefit by the traffic of those who click the link to read the entire thing (advertising for example).
Fair use means you can post parts of someone's work to critique it, but not the entire thing. Generally, textual works are subject to the fair use provision.
So, what are the limits of fair use? How much of an article can you post? DU uses "maximum 4 paragraphs" as a rule. Depending on the size of the article, and the average lengths of paragraphs, that number may be too high or too low. But it is a good starting point.
The other thing to consider is that many people will *not* read long posts of pure text. (Quotes, bullets, highlighting, and such make it more likely someone will at least skim the post for the good stuff.)
I think in the case of the Sirota article, the first 3 paragraphs covered the main point very well. And the beginning and end of the third paragraph are especially good:
By the end, Kerry had helped dismantle a massive criminal enterprise and exposed the infrastructure of BCCI and its affiliated institutions, a web that law enforcement officials today acknowledge would become a model for international terrorist financing. As Kerry's investigation revealed in the late 1980s and early 1990s, BCCI was interested in more than just enriching its clients--it had a fundamentally anti-Western mission. Among the stated goals of its Pakistani founder were to "fight the evil influence of the West," and finance Muslim terrorist organizations. In retrospect, Kerry's investigation had uncovered an institution at the fulcrum of America's first great post-Cold War security challenge.
So, those are some things to consider when using an article like this. But I am very glad you posted it - like I said above, it is an excellent article. Good find.