The only reason that would have made it acceptable would have been "game is losing more money than it's making".
Telling the truth, very clearly, as to why it was being canceled may also have helped (mindy you, I have a feeling the truth would have lured greater levels of anger.)
As Arcanavilled basically said: the entire subsidary thing is just a tax accountant thing and I dare bet has zero to do with the entire "realignment".
If the game still made money (and it WAS making money,) none of those are valid reasons to close shop.
Well, the thing is we have absolutely no clue as to what really happened. There are many possible reasons that are much more compelling than a simple "the game made money, but we'll close it out of malice anyway". For example here's one that I find quite entertaining:
In 2004 Marvel sues Cryptic on copyright and trademark grounds. The suit has been settled, but the public never learned what were the terms. All was good, though. We could enjoy our game and Marvel has even chosen Cryptic to develop an MMO for them.
Fast-forward a few years. Marvel is acquired by Disney, while also becoming the highest-grossing movie franchise (says Wikipedia
citing this source). It doesn't take long for Disney to start trying to capitalize on this success by releasing superhero flavored games of their own. The ones released thus far aren't true MMOs and probably can't be considered competion, but maybe a more traditional multiplayer RPG is also planned or at least pondered.
Enter City of Heroes. Despite its age, it still has a firm grasp on the market and not even DCUO with its venerable IP behind it is able to shake its position. Plus there is also CO. This niche is simply too saturated. So what does Disney do? It dusts the old settlement off and starts giving NCsoft the look.
Now NCsoft has had a brush with the US legal system before and lost sizeable amounts of money as a result. They were asking for it, sure, but it remains true that they were burned by it painfully. And now they may be on the eve of yet another legal nightmare with a ten ton legal gorilla poised against them, fighting on its own home turf. What are the chances? Plus the subject is an eight year game that may be a gem and which is still profitable, but not by a large margin. And it so happens that they are also in the midst of realigning their western subsidiaries. The route of least resistance for NCsoft would now be to close all the operations and seal the IP, so it doesn't attract any more problems and just give the whole thing a rest. It's no longer worth the effort in their opinion. There will be some outcry from the most dedicated fans, but it all should be manageable.
The studio behind the game suddenly becomes a hot potato too, as not only at least half of their staff, head management included, is still actively working on CoH, but they are also actively pitching CoH2 - a game that would attract the same kind of trouble. It makes sense to let them go as well. And there. This problem solved. Only gazillion others, diving stock price included, to go.
Did this really happen? Hardly likely. However it illustrates my point - until we know all the facts, we can't really be sure why the closure happened. And claiming with certainty that it was a simple spite or a whim is just as unfounded as my conspiracy theory above. It happened. For reasons. We don't know them, but they are there.