Normally it wouldn't really prove anything that they don't go after apostates, since it's not always worth the time and expense for institutions to go after people on the internet. But since the WTS normally likes to go after any perceived violation of their rights, it does stand out.
There is also the issue of opinion. Opinions are usually protected, even if they might be able to fairly be characterized as a "lie". For example, let's say that I write that the GB is more interested in protecting pedophiles than protecting children. Even assuming for argument's sake that it's false, there wouldn't be legal grounds since there's no way to prove what they really are interested in.
It's an interesting point. I don't know how active JWs would react to this. I suspect it would have to be someone who already has doubts. Otherwise, I doubt most JWs understand this concept and will just assume there is a good reason the WTS doesn't pursue these people. When it comes to legal matters, they like to sound the trumpets whenever they get a victory but when they lose they say it's because we're in Satan's world and everything is under his control.