How long did it take to fix the issue? Assuming that it is a simple task to fix, then why was it not fixed when I reported it on May 26th nor when I reported it again on June 24th?
Note the irony of http://google.com/safebrowsing triggering a Facebook "unsafe link" security warning. Looks like the code is using a substring match, which might be incorrect logic.
Could you provide disclosure regarding how this categorization system works?
I don't think there's a problem with parsing the URL because it clearly is able to load up the preview. All I can say is, MAN! They really don't want you helping people with Tor.
Any sane debugging process should proceed beyond this stage. :-)