According to the law and from the perspective of the business world, what Mr. Li & co. are doing is perfectly fine, no one would disagree. You call it 'legitimate', and I think that's a fair description.
Obviously, though, you'll notice that a lot of people don't like what they're doing. I personally wouldn't go so far as to call it 'unethical', but I know that I definitely don't agree with what they do, since on a number of levels it strikes me as wrong.
The legal framework surrounding the purchase and ownership of domain names was ultimately established by fiat. The model we have is not a sacred construction that fell out of an economics textbook. It was chosen to represent some idea of how we thought domain name ownership should be handled. We didn't know how the domain name market was going to evolve. How could we? It was a radically new idea with little precedent. The closest thing we had was our model for physical real-estate, and so that's roughly what we adopted, in an attempt to make it a fair system.
Early on, though, we realized that our model didn't quite match up to the expectation of fairness we had for our system, and when a legal framework fails to match our conception of how things should work, we revise it, and we do so with more laws. The major law that came out of this was the Anticybersquatting act, and though it was drafted largely as a result of corporate interest, it represents our belief that something was wrong with the framework we had set up. (If I'm going to build a McDonald's, you have to move your lemonade stand off the piece of real estate labeled MCDONALDS in big bold letters...on every map ever printed.)
When you say that Mr. Li isn't a cybersquatter, even though it is grossly obvious he fits that definition (http://en.wikipedia.org/wiki/Anticybersquatting_Consumer_Pro...), whether you agree with it or not, it leads me to believe that you have a problem with anyone being labeled a 'cybersquatter', on the basis that there is nothing inherently wrong with the act of cybersquatting.
The problem people have with Thomas Li and octopart.cn, is not that he desires to own a domain name that somebody else might want. It's that, rather than engage in some type of productive behavior, Mr. Li has seized upon a opportunity to make a little money entirely at the expense of the Octopart company. His behavior is counterproductive. It is of benefit to no one (except himself). He has created, in effect, a potential loss for Octopart, and now he is offering them the ability to avoid that loss. The key point here is that he has created a loss opportunity, and no real gain for anyone. Of course, he has the potential to gain money for himself, but in the long tradition of ill-gotten gains, people really won't like him for it, because he won't be receiving money in exchange for some positive output he's created, he'll be receiving ransom money in order to not make something worse.
We see a similar thing happening in the parking of domain names on a massive scale. Mass parking occurs when an entrepreneur buys up thousands of domains, on the cheap---since most of them haven't been registered---and then sets up dummy search pages and advertisements on each of them. He never puts original content on these sites. With judicious use of SEO tricks, he can still get them to pop up in your Google search, even though nobody in their right mind would ever link there or even want to visit there in the first place. Do parked domains actually add value for the consumer? Not likely. At best they simply rearrange or add vestigial segments to the plumbing of the internet. If I search for "sony tv" and the first ten results are WALMART.COM and the last one is TARGET.COM, my search isn't any better than if the first result was Wal-Mart and the second was Target. All Wal-Mart's done is increase the probability that I visit their site before I visit Target's...which may improve their market share, but actually degrades my experience as a consumer. You'll notice what we have going on is, again, a transfer of wealth, and not a creation thereof.
The practice of mass domain name parking must make some people a lot of money, but I don't think that anyone believes this is a desirable feature for the internet to have.
(Historically, these types of 'transactions' are frowned upon. If I'm a pirate and I capture your ship, I just got a lot richer, but the net effect on society is negative, since much work has been expended without the creation of wealth, and now much more work in the future will have to be expended on defense, which, short of economic stimulus and R&D, also fails to create wealth. This is why industrialized societies don't like war, or theft, or raiding, or vikings, bandits, bank and train robbers, burglars, pirates, muggers, hijackers, and highwaymen. Their acts are always lucrative for a small number of people at the severe expense of everyone else. Wouldn't you rather someone spend all day planning a building instead of a robbery?)