Stop a site from catching fake referers

[bugmenot]

Here's a challenge for you: haaretz.co.il usually only has previews of its articles. But it allows you reading full articles if you found them via an external site (e.g. Google).
Alas, it's smart enough to catch you if you only fake coming from an external site:

Code:

[HTTP headers]
In = FALSE
Out = TRUE
Key = "Referer: Fake haaretz (Out)"
Match = "?"
Replace = "https://www.google.com"

If you try this, the article's source code contains a code that seems to load http://hrz.haaretz.co.il/bots.js, which pops up a message and forwards you away from the article. Note it's not the bots.js that's found in the source code. And it loads even if you block it.

You can test it on this article:
http://www.haaretz.co.il/opinions/.premium-1.2001807
Which works when you enter it via Google:
http://www.google.com/url?sa=t&rct=j&q=&...vEdabu1M2w
Or via Twitter:
http://t.co/dVLOjy5znp
Or via Facebook (you must be logged in):
http://www.facebook.com/l.php?u=http%3A%...anp2Pe&s=1

So how does it differ real referrers from fake ones? How can bots.js be loaded when you block it?