While what your saying is true, I don't think it applies in this case. I think the rumor sites are just that, rumor sites. They are just as often wrong as right. Often, they are wildly off the mark. Therefore, your criteria for journalistic integrity should not apply, though ThinkSecret should acknowledge that its information may not be factual, and should not represent itself as a "hard" news site.
I don't think the case has merit. I'm no legal expert, but as far as I can tell, ThinkSecret is merely reporting information passed on to them by others. They are not breaking in and stealing information. They are not (afaik) paying for information. They are also not a direct competitor, seeking to use the information for direct competitive advantage. Again, afaik, they are just passing on rumors. It seems that the problem is with Apple employees, affiliates or others with inside knowledge leaking the information. Of course, assuming they signed nda's (which Apple is religious about making people sign, at least they always made me sign

), or are otherwise contractually obligated to keep this information secret, Apple has very good reasons(which you touched upon in your post) to go after them. Unfortunately for Apple, I don't think ThinkSecret signed any nda's.
Frankly, I think that Apple is fishing for names. Or looking to scare ThinkSecret. Or its a publicity stunt. For example, the flash ipod story was, if I remember correctly, broken by a Wall St. stock analyst some months ago. Does that mean that they(the brokerage) should be the subject of a lawsuit? Seems doubtful. I also think that this attention is partly due to "legitimate" news services like Reuters and AP picking up the rumor stories. Which happens to be a result of Apple actually becoming relevant to the mainstream press again. The iPod was the Tickle Me Elmo this past Christmas and Apple controls the entire segment. Everyone is scrutinizing Apple.
Having said that, I will say that the rumor reporting this time has been unusual. One, there has been a whole slew of rumors. I can't remember the last time there were so many major announcements being reported. Monitor price drops, iWork, Pages, flash iPod, headless imac, new server products...used to be everyone got excited if Apple announced a speed bump for the iMac. And second, the information ThinkSecret and others are getting is pretty damn good. Whoever the source is, he is definitely in the know.