Not just the anti jw internet sites, but the internet by itself helps people gather information from many sources. Reason and logic kick in and vola!
Unfortunately, the internet is just as efficient at disseminating cult propaganda, fake-news and misinformation. In fact, it's probably more of that now than the dry information resource it once was (if ever, maybe it's rose-tinted spectacles).
If the internet was truly an inoculation against cults, then they would cease to exist but the reality is they are thriving.
The Mormons advertise in the programme for the show The Book of Mormon that ridicules them. It's all just publicity and however much negative information there is about them, someone will find it appealing and sign-up or else they wouldn't advertise.
I don't think the internet is the threat to them that many imagine which is why they are now embracing and using it as well.
The thing it is good for is allowing communication and support networks for people who do decide they want to leave (plus the information to help them make a confident informed choice).