I agree that viewing the suing MtG judges as unethical is a bit warped, and I hope their lawsuit is successful.
However, I wouldn't characterize WotC's role as lying to the judges, or somehow willfully taking advantage of them. Gaming cons, competitions, and tournaments have a long history of being volunteer run, because gaming is an industry that started at the grass-roots level and volunteerism is really the only way gaming tournaments could have been run in the old days. WotC and MtG has long outgrown that, IMO, and shouldn't be using volunteers anymore to run their tournaments . . . but for them to continue doing things as they always have is somewhat understandable, until it's made clear to them this isn't going to work in today's environment.
My assumption is that the judges suing WotC realized that the responsibilities they were given, and how they were treated by WotC, really put them in the category of unpaid employee rather than volunteer, and so most likely DID approach WotC first to try and change that situation. WotC has been using volunteers since day one, and why give that up to spend more money paying people fairly, especially when volunteers are likely somewhat plentiful? The judges likely saw that as putting profits over people (as do I), while WotC likely saw things differently. I doubt folks at WotC feel like they are taking advantage of the judges (at least, I hope not!). So, to court we go! Two opposing parties, both feeling in the right, happen all the time in court battles, of course.
Hopefully WotC will see the light, either through a settlement or forced by court order. This WILL change how cons and tournaments are run, but mostly on the highest levels. Cons and tournaments that need to continue relying on volunteers (because they are small-time) will need to be careful how much responsibility they put on their volunteers, and larger cons/tournaments will need to step up and actually hire some folks to shoulder the enormous amount of work required.