You make a good point; I don't think I can argue against what Octopart is trying to do from any kind of good vs. evil ethical standpoint. However, I can understand a business such as Digi-Key wanting to maintain control, and they could easily argue it is for the benefit of the customer. For example, when a customer searches Octopart, are they going to also get a list of complementary parts from each supplier? I doubt it. What about helpful charts, material safety data sheets, and CAD schematics? If someone was just scraping my site and hijacking the search functionality but failing to deliver the rest, I'm not sure I'd want my name attached either.
Of course this is really coming at it from the wrong level. The truth is that Digi-Key can simply ignore you, and it doesn't hurt them in the slightest. And while doing so, they can be sure they aren't reaping any of the negative consequences of being associated with you either.