Whether or not CK helped drive sales is immaterial: it's WotC's right AND duty to control it's IP. If they decided what CK was doing was a problem for them right now or could become one in the future, that's their perogative.
I haven't seen anyone arguing the contrary, so I'm not sure who you're preaching to, exactly; the choir is already singing.
The point of this entire thread seems to be to point out that ...
-- the move is easily seen as nothing but sheer pettiness, or as a knee-jerk reaction to the rather abysmal reception 4E has gotten from some people;
-- WotC was not losing profits due to CrystalKeep's site, as they'd already given up on profits when they gave up on the system;
-- WotC's IP rights were not (and still are not) in jeopardy due to CK or any similar sites;
-- WotC seems not to have considered any of the PR ramifications of this decision, which from a fanbase viewpoint, is one in a long line of incredibly stupid decisions;
-- the move is purposeless when torrent websites have effectively rendered any chances of preventing copyrighted material from being traded free of charge;
-- this act could actually do nothing other than lower the number of new and prospective 3.x players.
Just because you have a right doesn't mean exercising it on purpose is wrong.
If WotC had any "duty" to protect intellectual property rights, they would have exercised it many years ago by going after CK and similar sites and shutting them down. Those sites have been up far too long for WotC to claim with a straight face in open court that they'd done everything necessary to strenuously defend their copyright. I suspect the reason they never bothered before is because their lawyers have informed them they were in NO such danger.
If they were ... well, hell, they've already lost that copyright, and someone should file a suit about it.